Lightly shape ground beef into eight 1/2-inch thick patties. Place patties on grid over medium, ash-covered coals. Grill, covered, 11 to 13 minutes (over medium heat on preheated gas grill, covered, 7 to 8 minutes) until instant-read thermometer inserted horizontally into center registers 160°F, turning occasionally. Season with salt and pepper after turning. About 1 minute before burgers are done, top with cheese stars.