Heat grill. In large saucepan, combine all ingredients excepts buns. Bring just to a boil over medium-high heat. Reduce heat; cover and simmer 10 minutes. Remove bratwurst and if necessary, continue simmering onion until tender.
Immediately place bratwurst on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Cook 6 to 10 minutes or until browned, turning once. Drain onion; serve with bratwurst on buns.