HEAT oil in large skillet on medium-high heat. Add chicken; cook 6 to 7 min. on each side or until done (165°F). Remove from skillet; cover to keep warm. ADD peppers and onions to skillet; cook 3 to 4 min. or until crisp-tender, stirring frequently. Stir in tomatoes and A.1. RETURN chicken to skillet; simmer 3 to 4 min. or until heated through. Serve topped with sauce and parsley.