HEAT grill to medium heat.
MIX meat and barbecue sauce; shape into 4 (1/2-inch-thick) patties.
GRILL patties 4 to 5 min. on each side or until done (160°F). Top with cheese; grill 1 to 2 min. or until melted.
SPREAD buns with guacamole; fill with lettuce, cheeseburgers, tomatoes and onions.