Heat oven to 425º F. Line two baking sheets with tin foil.
Toss sliced bell peppers, onions and garlic with one tablespoon olive oil on one of the foil lined cookie sheets. Season with salt and pepper. Place in the oven.
Place chicken breasts on the other foil lined cookie sheet. Rub with 1 tablespoon olive oil. Season with salt and pepper then sprinkle with chili powder. Place in oven below peppers. Bake for 15-20 minutes or until internal temperature is 165 degrees and juices run clear. Peppers and onions will be lightly browned on the edges and tender.
Slice chicken breasts and serve with pepper mixture on tortillas with your favorite fajita toppings. Enjoy!