Prep Time: 15
Cook Time: 10
Serves: Serves: 4
Combine vinegar, sugar and salt in a medium saucepan. Bring to a simmer over medium heat, stirring constantly to dissolve sugar. Add onion; simmer 2 minutes. Drain well; transfer onion to a bowl and refrigerate to cool while grilling burgers.
Meanwhile, combine meat, 3 tablespoons barbecue sauce and pepper. Form into 4 patties, 5 inches in diameter and ½-inch thick.
Preheat grill. Grill patties 5 minutes per side or until no longer pink in center. Spread remaining 1/4 cup barbecue sauce over patties; top with cheese. Grill 1 minute or until cheese is melted.
Serve patties and pickled onion in rolls.