Drain chicken; discard marinade. Add chicken to skillet. (If necessary, add 1 tablespoon cooking oil during cooking.) Cook and stir for 4 to 5 minutes or until no pink remains. Return vegetables to skillet. Stir together salsa and chili powder. Add salsa mixture, corn, and beans to skillet. Cook and stir for 1 to 2 minutes more or until heated through. Serve with warm tortillas and cheese, if desired. (To heat tortillas, wrap in microwave-safe paper towels; micro-cook on high power for 30 seconds). Makes 4 servings.