Preheat oven to 425 degrees F. If using breasts cut in half lengthwise.
In a large baking dish, add chicken, garlic, salt and pepper. Mix well to coat evenly and spread in a single layer. Cover and bake for 20-25 minutes. Chicken is cooked when pale and surrounded by clear juices.
In the meanwhile, preheat large ceramic non-stick skillet on low-medium heat and swirl oil to coat. Add onion and saute for a few minutes, stirring occasionally. Add mushrooms and saute for a few more minutes, stirring occasionally. Add bell peppers and saute for 5 more minutes, stirring.
Remove chicken from the oven and turn broiler on High. Separate chicken a bit from each other and top each piece with vegetables (sprinkle around too) and top with cheese. Broil for 5 minutes or until cheese is melted.
Serve chicken hot with its juices over rice, quinoa or zucchini noodles. This chicken and peppers dish tastes cold amazing too!
Notes
Store: Refrigerate in an airtight container for up to 3 days. Reheat by baking with juices while covered for 10 minutes at 350 F.
Freeze: Freeze leftovers in an airtight container for up to 3 months. Thaw in the fridge overnight.