Place onion wedge kabobs on grid over medium, ash-covered coals. Grill, covered, 15 to 20 minutes, turning occasionally. (Gas grilling times remain the same.) About 10 minutes before onions are done, move kabobs to outer edge of grid. Place beef kabobs in center of grid; grill, covered, 8 to 10 minutes (over medium heat on preheated gas grill, 9 to 11 minutes) for medium rare (145°F) to medium (160°F) doneness, turning once.