HEAT grill to medium heat.
COOK and stir onions and garlic in margarine in medium skillet on medium heat 5 min. or until tender but not browned; stir in sugar. Simmer on low heat 10 min., stirring occasionally.
MEANWHILE, shape meat into 6 patties. Grill 5 min. on each side or until done (160°F).
STIR steak sauce into onion mixture. Fill rolls with lettuce, onion mixture and burgers.