Preheat oven to 425°F.
In a large bowl, add cut peppers and onions, seasoning them with salt, pepper and garlic with about 1 Tbsp of olive oil. Mix until combined.
Get out a large sheet pan and spread the peppers and onions flat on ½ of the tray.
Next, in a bowl add in chicken, olive oil and seasoning. Mix until the chicken is covered and spread on the other half of the sheet pan so every piece is flat to help cook evenly.
Bake in the oven for 30-40 minutes or until the chicken is at least 165°F and the peppers are roasted.
Preheat a pan large enough to fit your tortilla and add cooking oil.
Place the tortilla down carefully in the pan and let it cook while adding filling to ½ of the tortilla; using cheese first to “seal” the quesadilla.
Fold over top and press flat.
Let it cook until desired crispiness on both sides (flip to get both sides crispy) and remove from the pan carefully.
Let your quesadilla sit a minute or two to cool and serve with your favorite sauce or a dollop of sour cream. Enjoy!