In a large Ziplock bag, combine chicken with all the peppers and onion.
In a small bowl, whisk together olive oil, chili powder, cumin, garlic powder, salt, oregano, red pepper flakes and pepper. Pour over the chicken and pepper strips. Seal bag and shake until everything is well coated. Refrigerate for at least 30 minutes and/or up to a few hours. (*I like to let mine sit in the fridge about 2 hours.)
Preheat oven to 400 degrees F. Line a large cookie sheet with foil and spray with cooking spray. Spread seasoned chicken mixture onto the prepared cookie sheet.
Bake for 18 to 22 minutes or until chicken is cooked through.
Serve on flour tortillas with desired toppings.