MEANWHILE, cut steak into 1-1/4-inch pieces. Place steak, mushrooms and peppers in resealable plastic bag. Add marinade; seal bag. Refrigerate 30 min. to marinate.
PREHEAT grill to medium heat. Remove steak and vegetables from marinade; discard marinade. Alternately thread steak, mushrooms and peppers on skewers.
GRILL 10 min. for medium doneness, turning occasionally.