Doesn’t anybody use a search engine anymore?
https://www.straightdope.com/21341942/why-do-toasters-have-a-one-slice-slot
https://www.sandiegoreader.com/news/1998/mar/26/when-toasting-single-piece-bread-why-does-it-matte/
I have a search engine and used it before posting. I searched the Dope, too, and saw those options. My question is NOT why toasters have a “one-slice slot”; it’s why my toaster says using one slot only (EITHER slot) will produce toast that’s darker on one side.
Where I’ve seen that warning, I’ve presumed it’s to prevent the plastic container from melting.
I’m up for this. I’ve just decided I’ll have toast and peanut butter for lunch - just one slice. Will report back!
It’s a Keenstone. It had good reviews on Amazon. OK, in the name of science, I experimented. Toaster was set on 4 (out of 6).
Pushed down the lever with the toaster empty. Heating elements glowed on each side of each slot.
Put one slice of bread in one slot (There is no “one slice” slot.) Pushed down lever. Toast emerged toasty tan on one side, dark brown with traces of ebony on the other.
ETA: I don’t use a toaster oven because it’d take up too much counter space.
Are you saying that the same rules that applied to toast 50 years ago should apply today?
Report: I put one piece of bread on the right hand side of my newish Sunbeam toaster. On first pop, the side facing into the middle of the toaster seemed more browned, but the whole thing looked like it could use more time. I reversed the bread and lowered the lever again - the second time it popped, it seemed pretty evenly well-toasted.
So, results are inconclusive but suggest that toasting is fairly even. I’ll try again tomorrow on the other side.
A little bit off topic but I just want to pass along a good tip. When making a grilled cheese sandwich put both slices of bread in one toaster slot and toast lightly. When assembling the sandwich use the toasted sides for the inside of the sandwich. Grill as usual and you’ll have a nice crunchy sandwich.
Alec caused quite a run on the Sunbeam Radiant Toaster market earlier this year. What was probably a five dollar Goodwill item is now selling for $200-400.
Well he did buy three of them after all. 
Those were hard to find long before that. I always had my eye out for them at thrift shops and yard sales, and have found one (mine) in about fifteen years.
But one would think 375-F is 375-F whether it’s in a toaster oven or a big 'ol oven.
If a toaster oven was designed without internal heating elements, that would probably be the case. The inside of the toaster oven could then be consistently 375 everywhere. But with heating elements, it is going to be hotter closer to the element. With toaster ovens being so small, the food will be inches away from the elements and will be absorbing a lot of radiant (light energy) heat. Ovens also have internal heating elements, but the the food is farther away and will be absorbing less of the radiant heat. It’s similar to how if you hold paper very close to a flame, it will catch fire. But if you hold the paper farther away, the paper will be fine.
One way to make food packages safer in a toaster oven is to put some foil on the top and bottom. The foil will act as a heat shield and the food will be heated more from the surrounding air rather than the intense infrared heat from the heating elements. But the infrared heat is what helps with browning, so you may need to remove the foil after a while if you want the food to brown.
Thanks to the information and the results of Straight Dope Level scientific experiments, I’m now reasonably sure the two-slices-only thing is probably unique to this toaster. Since I don’t want to be constrained to two slices of toast–I’m all into, like, freedom, man–I’ve decided the toaster is going back.
Toasters take up a lot less counter space.
But you can’t bake potatoes in them. You can’t warm up croissants in them. And I bake my bagels, I don’t toast them, so I can only do them in a toaster oven.
Mine has a setting for toast and a button that lets you control the number of slices (3 is good for 2 slices of toast.) A toaster probably makes toast better than a toaster oven, but is pretty limited.
All you say it true, but for those of us with limited counter space, a toaster oven is simply not an option. If I had unlimited counter space, I’d have all kinds of appliances I do without now. Since I don’t, I have to choose, and a toaster oven takes a back seat to a toaster and a coffee maker. I don’t have room to even store a toaster oven.
"If a toaster oven was designed without internal heating elements, that would probably be the case. "
Well, if the elements weren’t internal, wouldn’t that make it a heater?
supposedly the heat in a toaster oven is too concentrated for the plastic tray … for some reason in a toaster oven the tray gets hotter faster than than the food … i
n the “enlightened 
” region i live in they call toasters “ghetto or hood” ovens because a lot of the people in public type of housing supposedly will not have a working stove or oven (or even the gas turned on) but will have a toaster oven that the 10-year-old knows how to use better than the mom
We use a toaster oven that takes up as much space as a medium size 2-slice toaster, and we used to have one that took up as much space as a small 2-slice toaster (I don’t think they are available here now).
I see large toaster ovens in the shops, but I also see 3 sq ft toasters.