I'm not a huge fan of jarred sauces, but in a pinch you gotta do what you gotta do, so I stirred in half of this jar of Classico Tomato & Basil sauce......along with some minced fresh basil.
I spread the rest of the jar of sauce on the bottom of a baking dish, then laid the sliced chicken breasts on the sauce...
...and topped the whole thing with the peppers and onions in sauce mixture.
Finally, I sprinkled on a liberal amount of grated mozzarella cheese (tip: I keep grated cheeses like mozzarella and cheddar in the freezer - if you plan to cook with them they melt quickly in the cooking process and if you just plan to use them as is they will thaw quickly.).
I baked this entire casserole at 350 degrees for about 20 minutes - since everything was really already cooked this was just long enough for everything to melt and the flavors to come together. Serve it with your pasta of choice and a side green salad (I had arugula from my garden!) for a quick but satisfying weeknight dinner!