When you grill steak and vegetables, make a double batch so leftovers can be served in a sandwich. Top the steak with cheese and a sour cream-mayo dressing.
Place steak in large resealable plastic bag or glass dish. Add 1/2 cup of the marinade; turn to coat well. Refrigerate 30 minutes or longer for extra flavor.
Meanwhile, mix mayonnaise, sour cream and 1 tablespoon of the remaining marinade in small bowl. Cover. Refrigerate until ready to serve. Remove steak from marinade. Discard remaining marinade.
Grill steak, peppers and onion over medium-high heat 6 to 8 minutes per side or until steak is desired doneness and vegetables are tender, brushing with remaining marinade. Toast rolls on the grill, open-side down, about 30 seconds. Slice peppers and separate onion into rings. Slice steak into thin slices.
To serve, spread rolls with mayonnaise mixture. Top with steak, peppers, onion and cheese.