1. Heat greased grill to medium heat. 2. Mix all ingredients except Singles and buns just until blended; shape into 4 (1/2-inch-thick) patties. 3. Grill 5 to 6 min. on each side or until done (160ºF), topping burgers with Singles and adding buns, cut sides down, to grill for the last minute. 4. Serve burgers in buns.