Pre-heat oven to 400F. Grease a large baking sheet with cooking spray or olive oil and set aside.
Place chicken and fajita spices in ziplock bag or large bowl and combine until chicken is fully coated.
Heat 1 tablespoon oil in a large heavy-duty pan for at least 2 minutes. Add the chicken and cook on medium-high heat for 5-6 minutes on each side or until cooked through. Cool for 4-5 minutes then chop into small pieces.
Remove chicken from the pan and add the sliced onion and bell peppers to the same pan. Cook on high heat for 2-3 minutes or until lightly charred.
Place the tortillas on the sheet pan and fill each half with 1/4th of the chicken mixture, 1/4th of the bell pepper mixture and 1/4 cup of cheese. Fold and spray with cooking spray.
Bake for 10 minutes, flip and bake for 10 more minutes. Remove from oven and serve immediately while hot. We like to dip them in salsa, sour-cream or guacamole. Enjoy!