1In medium bowl, toss chicken and fajita seasoning. Spray 12-inch skillet with cooking spray; heat over medium-high heat. Add chicken and onion; cook 3 minutes, stirring frequently. Add bell pepper; cook 5 minutes longer, stirring frequently, until chicken is no longer pink in center and vegetables are crisp-tender.
2On each of 4 plates, place 1 tortilla; top each with 1 cup chicken mixture and 2 tablespoons salsa. Sprinkle with avocado and cilantro. Fold tortilla over filling. Serve with sour cream.