Step 1) Heat oil in large skillet on medium heat. Add chicken, onion, and pepper; stir fry until chicken is no longer pink and vegetables are crisp and tender, about 3 to 5 minutes. Stir in oregano, garlic salt, cumin, salt and pepper.
Step 2) Fill warm tortillas with chicken mixture. If desired, garnish with avocado, cilantro, and lime wedges.
TIP: 1 pound of skirt steak or flank steak may be substituted for the chicken.