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Mueller 4 Slice Toaster Oven vs Cosori Air Fryer Toaster Oven Side-by-Side Comparison

Alan Nguyen
Reviewer
Nguyen Ntk
Visual Specialist
Updated
Tested Using Methodology v1.0
Updated Apr 3, 2023
Tested Using Methodology v1.0
Updated Apr 3, 2023
The front of a closed stainless steel Mueller MT-175 4-Slice Countertop Toaster Oven on a white background.
The front of a closed Cosori CO130-AO 30L 12-In-1 Dehydrator Air Fryer Rotisserie Toaster Oven on a white background.

Our Verdict

6.1
Overall Score
  • Performance (50%)
    7.0/10
  • Design (25%)
    5.3/10
  • Usability (25%)
    5.2/10
8.4
Overall Score
  • Performance (50%)
    8.0/10
  • Design (25%)
    9.4/10
  • Usability (25%)
    8.3/10

The battle between the Mueller 4 Slice Toaster Oven (MT-175) and the Cosori Air Fryer Toaster Oven (CO130-AO) is an interesting one between our best-value small pick and our definitive best-to-buy pick. Without a doubt, the Cosori is the winner, but comparing it with the Mueller really highlights the strength of each unit.

Design-wise, the Mueller has a good overall build quality encompassing its detachable crumb tray that’s extra useful for cleaning the interior of a small toaster oven. Its control dials are also very precise for being analog.

The Cosori, on the other hand, has an intricate control panel with an informative digital display, intuitive buttons, and toggle switches for convection settings, lighting, and temperature conversion. On top of a larger capacity, these features, of course, make the Cosori cost a few times more than the Mueller.

What’s really impressive about the Mueller is its performance in spite of the common weaknesses of small units. Despite a lower power draw, the oven managed to keep up with the Cosori in toasting bread and baking pizza (though with a longer cooking time).

Nonetheless, the Cosori’s simply too good at roasting whole chicken and air-frying fries, utilizing its additional accessories including a rotisserie kit and air fryer basket.

Good Heat Distribution

Mueller 4-Slice Toaster Oven Performance

Performance
7.0
Performance Scores
  • Toast (40%)7.5/10
  • Pizza (25%)7.6/10
  • Whole Roasted Chicken (25%)7.0/10
  • Baked French Fries (10%)3.6/10
8.0
Performance Scores
  • Toast (40%)7.6/10
  • Pizza (25%)7.6/10
  • Whole Roasted Chicken (25%)8.9/10
  • Baked French Fries (10%)8.1/10
7.5

Toast

7.6
Mueller 4 Slice Toaster Oven Toast Test
From left to right, 24 pieces of toast for the top and bottom of three toast levels including lighter, medium, and darker.
The top and bottom of the best four pieces of toast from the stainless steel Mueller MT-175 4-Slice Countertop Toaster Oven.
On the left are the top and bottom of four pieces of toast from the first batch, and on the right are from the second batch.
Taste: 8
50% * 8 = 4.0
Even Surface Color: 7
20% * 7 = 1.4
Consecutive Usability: 7
30% * 7 = 2.1
  • Function: Toast
  • Number Of Slices: 4
  • Toast Level: ⅓ to Dark
  • Cooking Time: 4m
  • Second Batch: 4m
  • Convection: No

For our Toast test, we started off by trying the Medium Toast setting which was around 3 minutes 5 seconds on the timer. The four pieces of bread on the upper tray level came out only lightly toasted on top except for one golden brown piece. We then cranked it up to the Dark Toast setting—around 4 minutes 50 seconds on the timer—which, unfortunately, burnt the toast a bit.

Finally, we opted for the middle ground which was 4 minutes on the timer—⅓ of the rotation from Medium to Dark. This setting was tricky to get right on the time dial, so we used an external timer. It gave us the best possible toast results from this oven scoring a 7.5/10 in total.

After 4 minutes of toasting, the four pieces of toast had pretty good surface color. However, the colors varied from light golden to golden brown on both the top and the bottom, so we could only give a 7/10.

Luckily, the varied colors partially meant varied textures which were all good and deserving an 8/10. The golden brown areas had a more crispy outside while the light golden areas had a softer inside. Our head chef Tuyet Pham determined that it would go great with omelets, eggs benedict, and sandwiches but not so much with soup.

After taking out the first batch, we immediately put four more pieces inside to test the oven’s consecutive usability which ended up at 7/10. Also under the identical toasting time, the four pieces of bread became brown with an increased evenness from the first batch. While the color was a bit darker than ideal, the extra crispiness made the second batch more suitable for soups.

Cosori Air Fryer Toaster Oven Toast test
Cosori Air Fryer Toaster Oven Toast From left to right, 24 pieces of toast for the top and bottom of three toast levels including lighter, medium, and darker.
The top and bottom of the best four pieces of toast from the Cosori CO130-AO 30L 12-In-1 Dehydrator Air Fryer Toaster Oven.
On the left are the top and bottom of four pieces of toast from the first batch, and on the right are from the second batch.
Taste: 8
50% * 8 = 4.0
Even Surface Color: 8
20% * 8 = 1.6
Consecutive Usability: 6.8
30% * 6.8 = 2.0
  • Function: Toast
  • Number Of Slices: 4
  • Toast Level: 2/7
  • Cooking Time: 5m 49s
  • Second Batch: 3m 50s
  • Convection: No

We started our Toast test with four pieces of white bread. We ran the toast function at level 3. The results were good, but the color was a bit too brown to be ideal. After examining the outcome on level 2, it was clear that was the best option, earning a score of 7.6/10 in total. We also tried toasting at level 1, which resulted in lightly toasted bread, for reference.

At level 2, which automatically set the timer for 5 minutes 49 seconds, the four pieces of toast mostly had a beautiful golden brown color. However, the existence of lighter areas, especially on the bottom side, kept it from being perfect. We considered it worthy of an 8/10 for even surface color.

The taste deserved another 8/10 thanks to the toast’s crispy surface and soft, moist interior. Our head chef, Tuyet Pham, determined the toast would complement pretty much anything, including sandwiches, omelets, eggs benedict, and soup.

After the first batch of toast, we immediately placed the second batch in the oven. The toast level 2 program automatically reduced the time to 3 minutes 50 seconds to account for the last batch’s residual heat.

However, this seemed like too much of a reduction, since the toast came out mostly lacking in color. It wasn’t very crispy either, so we could only give the oven a 6.8/10 for consecutive usability.

7.6

Pizza

7.6
Mueller 4 Slice Toaster Oven Pizza Test
 Mueller 4 Slice Toaster Oven PizzaA toaster oven baked 9-inch thick-crust meat pizza with cheese, onions, and green bell peppers on top inside a baking pan.
Two slices of oven baked 9-inch thick-crust meat pizza with cheese, onions, and green bell peppers on top of one another.
Two hands break apart a slice of pizza with cheese, meat, onions, and green bell peppers on top baked using a toaster oven.
Cooking Time: 6
20% * 6 = 1.2
Crust: 8
20% * 8 = 1.6
Toppings: 8
30% * 8 = 2.4
Taste: 8
30% * 8 = 2.4
  • Function: Toast
  • Temperature: 450°F
  • Cooking Time: 9m
  • Convection: No

For its low power draw, the Mueller did pretty well in our Pizza test with a score of 7.6/10.

The oven took 9 minutes to bake a 9-inch thick-crust meat pizza which was slightly faster than the label’s recommended 10 minutes. However, compared to our tested toaster ovens, it could only be a 6/10.

The crust had a golden color all the way through and the inside was still moist. If only the crust was a bit more crispy, it would’ve gotten higher than an 8/10.

The toppings were also caramelized quite evenly from the meat and veggies to the cheese, worthy of another 8/10. The cheese was nicely melted but the areas closer to the back of the cooking chamber were more caramelized compared to the rest.

With both the crust and the toppings being 8/10, our chef had no reason to give the pizza one final 8/10 for taste.

Cosori Air Fryer Toaster Oven Pizza test
Cosori Air Fryer Toaster Oven PizzaA toaster oven baked 9-inch thick-crust meat pizza with cheese, onions, and green bell peppers on top inside a baking pan.
Two slices of oven baked 9-inch thick-crust meat pizza with cheese, onions, and green bell peppers on top of one another.
Two hands break apart a slice of pizza with cheese, meat, onions, and green bell peppers on top baked using a toaster oven.
Cooking Time: 10
20% * 10 = 2.0
Crust: 7
20% * 7 = 1.4
Toppings: 7
30% * 7 = 2.1
Taste: 7
30% * 7 = 2.1
  • Function: Bake
  • Temperature: 450°F
  • Cooking Time: 3m 30s
  • Convection: Yes

The Cosori’s ability to maintain a high temperature really shined in our Pizza test, garnering a score of 7.6/10.

With a high power output and powerful convection system, it only took 3 minutes 30 seconds to bake a 9-inch thick-crust meat pizza placed on tray level 2. This was extremely fast and deserving of a 10/10, the same as the Cuisinart TOA-60 which has the current highest pizza score.

However, the short cooking time resulted in uneven heating in the pizza crust and toppings.

While the bottom right quarter of the crust was golden brown, the rest didn’t have much color. Only that well-cooked part was crispy while the rest was soft, so we gave the crust a 7/10.

The same happened to the toppings. The bottom right quarter had a lot of caramelization—to the point that the onions even charred—while the rest was only mildly caramelized. In addition, the cheese wasn’t very melty, so we gave the toppings a 7/10 as well.

Taste-wise, our chef said it would be better if it weren’t for the slight bitterness from the charred onions. She gave the pizza another 7/10.

7.0

Whole Roasted Chicken

8.9
Mueller 4 Slice Toaster Oven Whole Roasted Chicken Test
A whole roasted chicken using the Mueller MT-175 Toaster Oven backside up on a silver baking pan on a white background.
A whole roasted chicken using the Mueller MT-175 Toaster Oven belly up on a silver baking pan on a white background.
A tray of whole toaster oven roasted chicken. The thermometer has two probes inside the chicken and displays 185°F and 192°F.
Eight pieces of a carved chicken including two carcass halves, two breasts, two wings, and two thighs on a baking pan.
Two hands pulling apart a roasted chicken thigh. In the white background is the rest of the roasted chicken on a baking pan.
Cooking Time: 6
20% * 6 = 1.2
Skin: 5.5
20% * 5.5 = 1.1
Doneness: 8.7
20% * 8.7 = 1.7
Taste: 7.5
40% * 7.5 = 3.0
  • Function: Toast
  • Temperature: 350°F
  • Cooking Time: 1h 20m
  • Convection: No

The Mueller could barely fit a 3 lb chicken for our Whole Roasted Chicken test. Nonetheless, the result was quite decent at 7/10 in total. If you were to purchase this oven and use it to roast a whole chicken, we recommend cutting it open or chopping it into pieces beforehand.

We first placed the chicken backside down on the baking pan. When we slid the pan in, the top of the chicken breast grazed the upper heating element’s guard and was seared.

After the first 40 minutes, we flipped the chicken to find out that parts of the skin on the back got stuck to the baking pan. Then, when we reinsert the pan, the same problem with the breast happened to the back. Luckily, they weren’t burnt.

However, even after 1 hour and 20 minutes, most of the chicken skin still hasn’t reached a desirable color. The chicken, for the most part, looked like it was steamed and not roasted, so we gave the skin a 5.5/10.

Nonetheless, our chef decided to stop the roasting as the color wouldn’t improve anyway and to avoid overcooking the meat. This cooking time was the equivalent of a 6/10 according to our data.

With such a long cooking time, the meat had no pink spots. However, the chicken’s internal temperature was 185°F-192°F, higher than the USDA recommended 165°F-180°F. Thus, we gave it an 8.7/ for doneness.

While not the most appetizing looking, the meat was very juicy. That, combined with the slight caramelization on the skin, was enough for a 7.5/10 for taste from our chef.

Cosori Air Fryer Toaster Oven Whole Roasted Chicken Test
A whole roasted rotisserie chicken using the Cosori CO130-AO Oven backside up on a grey baking pan on a white background.
A whole roasted rotisserie chicken using the Cosori CO130-AO Oven belly up on a grey baking pan on a white background.
A tray of whole toaster oven roasted chicken. The thermometer has two probes inside the chicken and displays 178°F and 181°F.
Two hands pulling apart a roasted chicken thigh from the carcass. In the white background is the rest of the roasted chicken.
Eight pieces of a carved chicken including two carcass halves, two breasts, two wings, and two thighs on a baking pan.
Cooking Time: 10
20% * 10 = 2.0
Skin: 8.5
20% * 8.5 = 1.7
Doneness: 9.9
20% * 9.9 = 2.0
Taste: 8
40% * 8 = 3.2
  • Function: Rotisserie
  • Temperature: 350°F
  • Cooking Time: 40m
  • Convection: Yes

We’ve conducted our Whole Roasted Chicken test a great many times, and the Cosori wasn’t the only one with a high power output and powerful convection system. What set it apart was its rotisserie kit and function.

In addition, the large cooking chamber had more than enough space for a 3 lb chicken to rotate smoothly with a baking pan below to catch the drippings, unlike the Instant Omni Plus 18L. Everything together scored a whopping 8.9/10.

The oven took only 40 minutes to roast the chicken to a beautiful color. That was the fastest time we’ve had so far, earning it a perfect 10/10. The skin was mostly golden with some appetizing golden-brown color at the wings and the tips.

However, it seemed like the skin cooked a bit too quickly and the fat wasn’t fully rendered, so the skin wasn’t very crispy. Nonetheless, the skin still deserved an 8.5/10.

What impressed us most was the near-perfect doneness—9.9/10—in such a short amount of time. The chicken had no pink spots and a consistent internal temperature of 178°F-181°F. It was basically spot-on to the USDA’s 165°F-180°F recommendation.

Unfortunately, for some reason, the meat wasn’t as juicy as we had expected. Combined with the less-than-crispy skin, our chef couldn’t give the chicken a higher score than 8/10 after tasting it.

3.6

Baked French Fries

8.1
Mueller 4 Slice Toaster Oven Baked French Fries Test
Mueller 4 Slice Toaster Oven Baked French FriesPieces of baked french fries using the Mueller MT-175 Toaster Oven on a grooved silver baking pan on a white background.
A close-up of pieces of baked french fries using the Mueller MT-175 Toaster Oven on a baking pan on a white background.
Ten pieces of broken-up baked french fries are stacked on top of pieces of whole fries on a grooved silver baking pan.
Cooking Time: 0
20% * 0 = 0.0
Color: 4.5
20% * 4.5 = 0.9
Texture: 4.5
20% * 4.5 = 0.9
Taste: 4.5
40% * 4.5 = 1.8
  • Function: Toast
  • Temperature: 400°F
  • Cooking Time: 27 m
  • Convection: No

Our Baked French Fries test brought out the Mueller’s weakness of not being able to maintain a high temperature due to its low power draw. Its even heat distribution couldn’t help much if the temperature wasn’t high enough, so the final score was 3.6/10.

We stopped the baking after 27 minutes as the fries weren’t getting any more colors. This, nonetheless, was over our time limit of 25 minutes, so it was a 0/10.

The fries had no significant color change and barely enough for a 4.5/10. We ended up with 12 oz of frozen fries that were more similar to being dried in an oven than being baked, so we gave them another 4.5/10 for texture.

Fortunately, the fries were cooked through and not soggy, so our chef could give them a 4.5/10 for taste and not a zero.

Cosori Air Fryer Toaster Oven Baked French Fries test
Pieces of baked french fries using the Cosori CO130-AO inside an air fryer basket on a grey baking pan on a white background.
A close-up of pieces of baked french fries using the Cosori CO130-AO inside an air fryer basket on a grey baking pan.
Eight pieces of broken-up baked french fries are stacked on top of pieces of whole fries inside an air fryer basket.
Cooking Time: 8.4
20% * 8.4 = 1.7
Color: 8
20% * 8 = 1.6
Texture: 8
20% * 8 = 1.6
Taste: 8
40% * 8 = 3.2
  • Function: Bake
  • Temperature: 400°F
  • Cooking Time: 17m
  • Convection: Yes

The Cosori took on our Baked French Fries test with its air fryer basket and scored an 8.1/10.

It took 17 minutes to bake 12 oz of frozen fries on tray level 2—quite fast compared to most. After comparing it with other units from our data, we gave it an 8.4/10 for cooking time.

The fries mostly had a great golden color with some of the thinner pieces looking the most appetizing. However, some thicker pieces weren’t as golden, so we gave the fries an 8/10 for color.

The same can be said about the texture of the fries, which earned another 8/10. Most of the fries were crispy on the outside and moist on the inside, but the thinner ones were a bit dry and the thicker ones weren’t crispy enough.

Overall, though imperfect, the fries were delicious enough to get one final 8/10 taste score from our chef.

Standard

Stainless Steel Mueller 4-Slice Toaster Oven Design Review

Design
5.3
design Scores
  • Exterior (20%)5.0/10
  • Interior (30%)1.0/10
  • Build Quality (50%)8.0/10
9.4
design Scores
  • Exterior (20%)9.0/10
  • Interior (30%)9.5/10
  • Build Quality (50%)9.5/10

In the Mueller MT-175 Small Toaster Oven Box

In the Cosori CO130-AO Box
A box, the Mueller MT-175 4-Slice Toaster Oven, a recipe booklet, a baking pan, an oven rack, a user manual, and a brochure.
  • Model: MT-175
  • Warranty: 1 year
  • User Manual
  • Baking Rack
  • Baking Pan

The Mueller toaster oven came in a basic packaging and positioned with two foam pads. The included accessories were simply duct-taped to the oven. Inside the box are also a user manual and a simple recipe booklet.

A box, the Cosori CO130-AO, rotisserie kit and lifter, air fryer basket, baking pan, oven rack, and 6 pieces of documents.
  • Model: CO130-AO
  • Warranty: 1 year
  • User Manual
  • Baking Rack
  • Baking Pan
  • Broiling Rack
  • Removable Crumb Tray
  • Rotisserie Kit and Lifter
  • Air Fryer Basket

The Cosori toaster oven was packed between two foam pads while all six of its accessories were wrapped in carton sheets and taped to the oven. Everything comes in an aesthetically pleasing box with minimal information on it.

All the documents you’ll need are inside a nice envelope. You get a user manual, a recipe book, and some quick references. You’ll also find a QR code leading you to the manufacturer’s website where you can register your product to extend your warranty by an additional year.

5.0

Exterior

9.0
A closed front of the stainless steel Mueller MT-175 4-Slice Toaster Oven with exterior measurements on a white background.
A closed front of the stainless steel Mueller MT-175 4-Slice Toaster Oven with exterior measurements on a white background.
Mueller 4 Slice Toaster Oven ExteriorThe front of a closed stainless steel Mueller MT-175 4-Slice Toaster Oven has a control panel and the right has holes.
The back and left sides of the Instant Omni Plus 18L have air ventilation holes. The back has a power cord and two buffers.
The top, front, and right sides of the Black+Decker TO1760SS 4-Slice Natural Convection Toaster Oven on a white background.
On a white background, the bottom of the Mueller MT-175 Toaster Oven has a detachable crumb tray, four stands, and holes.
The detached crumb tray of the stainless steel Black+Decker TO1760SS 4-Slice Countertop Toaster Oven on a white background.
  • Weight:
    9.0 lbs (4.1 kg)
  • Length:
    15.0" (38.0 cm)
  • Width:
    11.6" (29.5 cm)
  • Height:
    8.9" (22.5 cm)
  • Material:
    Stainless steel
  • Color:
    Gray
  • Door Handle:
    Cool-touch
  • Tray Indicators:
    No
  • Crumb Tray:
    Detachable

As simple as it is, the Mueller has all the standard exterior features of a small toaster oven but also something more. The bottom of the oven acts as a detachable crumb tray which not only makes it easy to remove the falling bits and crumbs but also to clean the entire interior.

The oven has a cool-touch door handle and back buffers to prevent it from being too close to the wall. Unfortunately, it has no cord storage or carrying handles.

Our measurements of the oven’s footprint were 14.96" x 11.61" x 8.86" which pretty much coincided with the manufacturer’s 14.84" x 11.85" x 8.86". However, the weight of the oven by itself was already 9 lbs whereas the label said the entire box was 7.63 lbs.

Cosori Air Fryer Toaster Oven ExteriorThe front of a closed Cosori CO130-AO 30L 12-In-1 Toaster Oven has a control panel and the right has ventilation holes.
Cosori Air Fryer Toaster Oven ExteriorThe front of a closed Cosori CO130-AO 30L 12-In-1 Toaster Oven has a control panel and the right has ventilation holes.
The back and left sides of the Cosori CO130-AO 30L 12-In-1 Toaster Oven have air ventilation holes. The back has a buffer.
On a white background, the top, front, and right sides of the Cosori CO130-AO Toaster Oven have air ventilation holes.
On a white background, the bottom of the Cosori CO130-AO Oven has a power cord, four stands, and air ventilation holes.
A closed front of the Cosori CO130-AO 30L 12-In-1 Air Fryer Toaster Oven with exterior measurements on a white background.
  • Weight:
    15.7 lbs (7.1 kg)
  • Length:
    20.0" (50.7 cm)
  • Width:
    17.3" (44.0 cm)
  • Height:
    12.6" (32.0 cm)
  • Material:
    Stainless steel
  • Color:
    Silver
  • Door Handle:
    Cool-touch
  • Tray Indicators:
    No
  • Crumb Tray:
    Removable

During our assessment, a prominent aspect of the Cosori toaster oven is the air ventilation holes on all sides of the casing to accommodate its powerful convection system. In addition, the glass door has indicators corresponding to the oven’s three tray levels and twelve cooking functions.

The oven doesn’t have carrying handles but it’s not heavy for its size so it’s not a big problem. Our measurements of 19.96" x 17.32" x 12.6" pretty much aligned with the manufacturer’s 20.1" x 16.5" x 12.5" with marginal differences being less than one inch. The difference in width is probably because we took the door handle into account.

Control Panel of the Small Mueller MT-175

Control Panel
The control panel of the Black+Decker TO1760SS 4-Slice Toaster Oven has 3 control knobs for temperature, function, and timer.
  • Type:
    3 control knobs
  • Temperature:
    150°F - 450°F
  • Timer:
    1 minute - 30 minutes + stay-on
  • Indicator Light:
    Yes
  • Status Bar:
    No
  • Light Toggle:
    No
  • Convection Toggle:
    No
  • Rotation Toggle:
    No
  • Automatic Preheat:
    No
  • Audio Cues:
    No

The Mueller has a basic analog control panel with three dials for temperature, function, and time. The time dial has a stay-on setting to help with its short range, similar to many other small toaster ovens. Interestingly, while the max temperature setting was 450°F, we actually recorded the internal temperature of the oven reaching 500°F on the said setting.

Cosori Air Fryer Toaster Oven Control Panel
  • Type:
    LED display + 2 control knobs + 3 buttons
  • Temperature:
    80°F - 450°F
  • Timer:
    1 minute - 6 hours + 12 hours + 24 hours
  • Indicator Light:
    Yes
  • Status Bar:
    Yes
  • Light Toggle:
    Yes
  • Convection Toggle:
    Yes
  • Rotation Toggle:
    No
  • Automatic Preheat:
    Yes
  • Audio Cues:
    No

The Cosori Air Fryer Toaster Oven has 2 control dials, one for functions and one for both timer and temperature. It also has 3 buttons, one for both the interior light and the temperature conversion, one to deploy the convection system, and one Start/Cancel button which lights up when the oven is running.

The LED screen will display ‘E1’ when there’s an open circuit in the temperature monitor and ‘E2’ for a short circuit.

Cooking Functions

The function dial of the Black+Decker TO1760SS 4-Slice Toaster Oven has 3 cooking functions including Bake, Broil, and Toast.
  • Toast
  • Bake
  • Broil
  • Keep warm

Different from most other toaster ovens, the Mueller’s Bake function only uses the lower heating elements as opposed to lower and upper. The Broil function still uses only the upper heating elements.

The Toast function is where both the lower and upper heating elements work. Nonetheless, the oven still provides all the basic functions for its intended purposes.

  • Toast (level 1-7)
  • Bagel (level 1-7)
  • Pizza (150°F - 450°F, 1 minute - 6 hours)
  • Bake (150°F - 450°F, 1 minute - 6 hours)
  • Roast (150°F - 400°F, 1 minute - 6 hours)
  • Air Fry (150°F - 400°F, 1 minute - 6 hours)
  • Broil (150°F - 450°F, 1 minute - 6 hours)
  • Cookies (150°F - 450°F, 1 minute - 6 hours)
  • Rotisserie (150°F - 400°F, 1 minute - 6 hours)
  • Dehydrate (100°F - 180°F, 30 minutes - 24 hours)
  • Ferment (80°F - 110°F, 30 minutes - 12 hours)
  • Warm (140°F - 230°F, 1 minute - 12 hours)

Besides the basic cooking functions, which already have a wide time and temperature range, the Cosori air fryer toaster oven also has various practical additional cooking functions allowing for even wider time and temperature ranges.

The ones that impressed us the most were Warm, Dehydrate, and Ferment which can maintain the oven at as low as 140°F, 100°F, and 80°F respectively. Looking at a number of recipes, these temperatures fit their intended purpose, which means this oven can act as a family-sized dehydrator and dough proofer.

Note that only the bottom heating elements operate during these functions.

1.0

Interior

9.5
Mueller 4 Slice Toaster Oven InteriorThe Mueller MT-175 4-Slice Toaster Oven’s cooking chamber has 2 quartz heating elements with guards and 2 guide rails.
Mueller 4 Slice Toaster Oven InteriorThe Mueller MT-175 4-Slice Toaster Oven’s cooking chamber has 2 quartz heating elements with guards and 2 guide rails.
The Mueller MT-175 Oven has 1 bottom heating element with a guard and 2 guide rails on its right cooking chamber wall.
  • Heating Elements:
    2 quartz
  • Convection Fan:
    No
  • Lighting:
    No
  • Tray Levels:
    2
  • Rotisserie:
    No
  • Safety Hook:
    No

Similar to many other small toaster ovens, including the Comfee CFO-BB101, the Mueller lacks a convection fan and an interior light. In addition, it only has two heating elements which can usually lead to uneven heat distribution compared to four or more heating elements.

These heating elements are made of quartz which uses infrared light to cook foods faster than the more common nichrome counterparts. Quartz heating elements also cool down faster, are more energy-efficient and easier to clean but not as durable.

However, if grease splashes onto the heating elements while cooking, it’ll leave permanent stains. This is why they usually have guards which this oven also has.

The Cosori CO130-AO’s interior has 4 heating elements, 3 levels, a rotisserie socket and bracket, a light, and a fan cavity.
The Cosori CO130-AO’s interior has 4 heating elements, 3 levels, a rotisserie socket and bracket, a light, and a fan cavity.
The Cosori CO130-AO Oven has 4 heating elements, 3 guide rails, and a rotisserie socket on its left cooking chamber wall.
The Cosori CO130-AO has 3 guide rails, a light, a rotisserie bracket, and a fan cavity on its right cooking chamber wall.
  • Heating Elements:
    4 nichrome
  • Convection Fan:
    Yes
  • Lighting:
    Yes
  • Tray Levels:
    3
  • Rotisserie:
    Yes
  • Safety Hook:
    No

The interior features include a convection fan, light, a rotisserie socket and bracket, three tray levels, and four nichrome heating elements. To be nitpicky, we think it’s a shame it doesn’t have a non-stick coating, so it may accumulate some stubborn stains.

Capacity of the Mueller 4-Slice Toaster Oven

Capacity of the Cosori XL 12-In-1 Air Fryer Toaster Oven
An opened front of the stainless steel Mueller MT-175 4-Slice Toaster Oven with interior measurements on a white background.
  • Length:
    10.6" (27.0 cm)
  • Width:
    9.8" (25.0 cm)
  • Height:
    7.5" (19.0 cm)

We could fit four slices of toast, a 9-inch pizza but we could barely fit a 3 lb chicken inside the Mueller, unlike the same-sized Breville BOV450XL. We measured the cooking chamber volume to be around 12.81 liters, slightly different than the manufacturer’s provided capacity of 11.67 liters. However, it could just be a difference in measuring standards.

An opened front of the Cosori CO130-AO 30L 12-In-1 Rotisserie Toaster Oven with interior measurements on a white background.
  • Length:
    14.2" (36.0 cm)
  • Width:
    13.8" (35.0 cm)
  • Height:
    9.8" (25.0 cm)

The Cosori has a spacious cooking chamber even compared to other large ovens. It can accommodate 6 slices of toast, a 13-inch pizza, or a 5-pound chicken.

We measured the volume to be around 31.49 liters compared to the manufacturer’s listing of 30 liters. The difference is minor and could just be a difference in measuring standards.

Power Cord

A two-pronged plug power cord. In the background is the stainless steel Mueller MT-175 4-Slice Countertop Toaster Oven.
  • Length:
    30.7" (78.0 cm)
  • Type:
    2-prong plug
  • Power:
    1100 W
  • Rated Output:
    120 V ~ 60 Hz

The power cord is 30.7 inches long, suitable for household use. Unfortunately, the oven doesn’t have any storage space for it.

A three-pronged plug power cord. In the background is the Cosori CO130-AO 30L Dehydrator Air Fryer Rotisserie Toaster Oven.
  • Length:
    40.9" (104.0 cm)
  • Type:
    3-prong plug
  • Power:
    1800 W
  • Rated Output:
    120 V ~ 60 Hz

The power cord has plenty of length for household use—roughly 40.94 inches. It protrudes from the bottom of the oven, unfortunately, so it may create awkward kinks now and then.

Baking Rack

Accessories

Baking Rack
A stainless steel baking rack of the Mueller MT-175 4-Slice Countertop Toaster Oven on a white background.
  • Length:
    10.5" (26.7 cm)
  • Width:
    8.8" (22.4 cm)
  • Height:
    0.5" (1.3 cm)
  • Material:
    Stainless steel
  • Dishwasher Safe:
    Yes

The two sides of the baking rack have slight curves upward at an angle to keep the baking pan in place. It fits perfectly with the guide to help prevent accidents when placing your food in the oven.

A stainless steel baking rack of the Cosori CO130-AO 30L 12-In-1 Dehydrator Rotisserie Toaster Oven on a white background.
  • Length:
    14.2" (36.0 cm)
  • Width:
    13.4" (34.0 cm)
  • Height:
    0.3" (0.7 cm)
  • Material:
    Stainless steel
  • Dishwasher Safe:
    Yes

The baking rack fits perfectly onto its guide rails to prevent accidents when placing food in the oven. It’s also shaped to maximize the space inside the cooking chamber.

Baking Pan

Accessories

Baking Pan
A grooved silver baking pan of the stainless steel Mueller MT-175 4-Slice Countertop Toaster Oven on a white background.
  • Length:
    10.2" (25.8 cm)
  • Width:
    7.9" (20.0 cm)
  • Height:
    0.6" (1.5 cm)
  • Material:
    Stainless steel
  • Dishwasher Safe:
    Yes

The baking pan doesn’t fit into the guide rails and has to on top of the rack. This may prevent the full use of the oven’s capacity and lead to some inconveniences during cooking.

On the bright side, the pan has ridges and grooves to give your food attractive roasting marks and catch the dripping better. It has a coating but is not completely non-stick so you may need to watch out for some stubborn stains after a hefty roast.

A grooved grey baking pan of the Cosori CO130-AO 30L 12-In-1 Dehydrator Rotisserie Toaster Oven on a white background.
  • Length:
    14.2" (36.0 cm)
  • Width:
    11.8" (30.0 cm)
  • Height:
    1.2" (3.0 cm)
  • Material:
    Stainless steel
  • Dishwasher Safe:
    Yes

The baking pan also fits the guide rails to fully utilize the cooking space. It has ridges and grooves which can give your food attractive roasting marks and allow drippings some space to flow away. Its coating isn’t completely non-stick, so it may gather some stubborn stains, though.

8.0

Build Quality

9.5
The front of an opened stainless steel Mueller MT-175 4-Slice Countertop Toaster Oven with an oven rack and baking pan.

For a simple small toaster oven, build quality is all about how durable it is and if it works properly. The Mueller accomplishes that with a sturdy stainless steel casing and smooth-turning dials.

The front of an opened Cosori CO130-AO Toaster Oven with a removable crumb tray, oven rack, baking pan, and air fryer basket.

The Cosori is made from high-quality and durable 304 stainless steel. The thick casing provides good insulation in addition to a well-thought-out convection system. Thus, the oven only gets hot to the touch after a long cooking time at a high temperature (>400°F).

As for the control panel, the LED display is very easy to see, the control dials turn smoothly, and the buttons are responsive. The accessories are designed to make the most out of the cooking chamber’s interior space.

Easy but Not Convenient to Use

Muller 4-Slice Toaster Oven Usability

Usability
5.2
usability Scores
  • User Control (30%)6.0/10
  • Ease of Use (50%)4.0/10
  • Cleanability (20%)7.0/10
8.3
usability Scores
  • User Control (30%)9.5/10
  • Ease of Use (50%)8.0/10
  • Cleanability (20%)7.5/10
6.0

User Control

9.5

Even though the Mueller only has three simple control dials, there are a few things to keep in mind. For the timer knob, when setting it to less than 10 minutes, always rotate past 10 minutes and then rotate back to the desired time.

It’s always tricky to precisely adjust time and temperature for an analog-control toaster oven and this one is no different. Nonetheless, you can use an external timer and an oven thermometer to get more accurate readings.

If you frequently use the stay-on feature, you can turn off the oven by rotating the function dial to Off instead of the timer.

The convection feature can toggle between normal and high, and neither setting makes much noise. The fan can run on all functions except Toast and Bagel.

Since time and temperature are controlled by a single dial, you must toggle between functions. Press the dial’s face to switch between them. Temperature can be adjusted in increments of 5°F or 2°C-3°C.

The timer, however, has different steps depending on the cooking function. For Pizza, Bake, Roast, Air Fry, Broil, Cookies, Rotisserie, and Warm functions, the timer can be adjusted in increments of 1 minute until it reaches 60 minutes, then in increments of 5 minutes from 1-2 hours, in increments of 10 minutes from 2-3 hours, and in increments of 15 minutes from 2-3 hours. For Dehydrate and Ferment functions, the timer only adjusts in increments of 30 minutes.

On top of the many practical cooking functions, the ease with which you can adjust time and temperature makes this oven, overall, simpler to use than many other digital ones. In addition, you can press and hold the time and temperature dial to turn off the display to save energy while you’re not cooking.

4.0

Ease of Use

8.0

What’s convenient about 100% analog toaster ovens is that it’s very simple to adjust time and temperature during cooking. When the timer runs out, a bell will sound and the oven will shut off. Afterward, you can freely leave it plugged in and not worry about power consumption as it has no digital display.

The door can open at any angle < 50° to let food cool down inside the oven. However, keep in mind that opening the door doesn’t stop the oven. The exterior shell isn’t very thick, so it gets hot to the touch quite quickly during cooking.

The Cosori has an automatic preheat phase which engages for the Pizza, Bake, Roast, Broil, Cookies, and Air Fryer functions. If the oven’s already hot, the function will recognize that fact and reduce its preheating time.

This toaster oven is one of the rare units that actually preheat to the input temperature. Most others simply heat to a hardwired preheat temperature that cannot be adjusted. 

According to our observation, the Cosori takes around 2-4 minutes to reach 300°F, 3-5 minutes for 325°F, 4-6 minutes for 350°F, and 6-8 minutes for 400°F. When preheating is finished, the oven will beep several times and the display will flash once every minute. You’ll need to press start to initiate cooking or the cooking function will be canceled after 10 minutes.

Thanks to the light toggle button, you have full control over when to turn the light on and off. The door can rest open at a 70° angle to allow food to cool inside the oven. Opening the door doesn’t stop the heating elements or the interior light.

The oven turns off automatically after 30 minutes of no interaction. Nonetheless, we still suggest unplugging it after use for safety reasons.

The Cosori’s EvenRapid Tech™ is advertised to reduce cooking time by 30% thanks to increased heat circulation. Suffice to say, it met our expectations with fast cooking times and even surface caramelization (except on our Pizza test).

7.0

Cleanability

7.5
Mueller 4 Slice Toaster Oven CleanabilityPermanent stains on the left cooking chamber’s ceiling and the upper heating element’s guard of the Mueller MT-175 Oven.
Mueller 4 Slice Toaster Oven CleanabilityPermanent stains on the left cooking chamber’s ceiling and the upper heating element’s guard of the Mueller MT-175 Oven.
Permanent stains on the right cooking chamber’s ceiling and the upper heating element’s guard of the Mueller MT-175 Oven.
The cleaned grooved silver baking pan of the stainless steel Mueller MT-175 4-Slice Countertop Toaster Oven.

We clean the stainless steel exterior with no problem. However, after the chicken test, there were burnt bits stuck to the upper heating element’s guard and grease on the cooking chamber’s ceiling. There was ample space between the ceiling and the upper heating element, so we proceed to try every cleaning method possible.

Unfortunately, we could only scrub off the bits. Due to the interior not having a non-stick coating, there were some permanent stains on the cooking chamber’s ceiling and the upper heating element’s guard.

Luckily, the heating element itself was intact. Also, we were able to remove the stubborn stains on the baking pan by brushing them with a paste of baking soda and water.

Cosori Air Fryer Toaster Oven CleanabilityGrease on the Cosori CO130-AO 30L 12-In-1 Dehydrator Air Fryer Rotisserie Toaster Oven’s cooking chamber ceiling.
Cosori Air Fryer Toaster Oven CleanabilityGrease on the Cosori CO130-AO 30L 12-In-1 Dehydrator Air Fryer Rotisserie Toaster Oven’s cooking chamber ceiling.
The cleaned cooking chamber’s right wall of the Cosori CO130-AO Toaster Oven with some stains behind the rotisserie bracket.
The cleaned grooved grey baking pan of the Cosori CO130-AO 30L 12-In-1 Air Fryer Toaster Oven with some stubborn stains.
The cleaned rotisserie forks of the Cosori CO130-AO 30L 12-In-1 Dehydrator Air Fryer Toaster Oven with some stubborn stains.

The Cosori’s exterior and interior are made of stainless steel, so they’re usually easy to clean. However, the interior doesn’t have a non-stick coating, so the grease from our whole roasted chicken test led to some extremely stubborn stains on the cooking chamber’s ceiling. We couldn’t completely remove them even after brushing them with a paste of baking soda and water.

The rotisserie forks and rod as well as the rotisserie bracket and the baking pan developed equally stubborn stains. On the bright side, it wasn’t difficult to clean caramelized bits of food from the air fryer basket despite the fishnet design.

The grease on the other walls and around the fan cavity was easy to clean. We were worried that grease might splash into the fan cavity, though.

We were able to easily remove fallen food scraps thanks to the removable crumb tray. However, we still had to tilt the oven to get them all out.