Pre-heat oven to 400°F. Combine spices in a small bowl. Set aside.
Layer the onions and peppers on a baking sheet. Top it with the chicken. Sprinkle the spice mixture and garlic over the chicken. Mix all ingredients together with olive oil. Spread the mixture evenly on the pan. Bake in the oven for 20-25 mins, turning halfway through.
For the last 5 minutes, place tortillas covered in foil in the oven to heat through. Mix the chicken and peppers in a bowl. Serve warm tortillas with your favorite toppings and sprinkle on cilantro.