Place patties on grill over medium heat. Cover grill; cook 11 to 13 minutes, turning once, until meat thermometer inserted in center of patties reads 160°F. During last 2 minutes of cooking, top each patty with cheese and place buns, cut sides down, on grill. Cook until cheese is melted and buns are toasted. Remove burgers and buns from grill; cover to keep warm.