It can be hard to tell when your brat is cooked through on the grill, so instead of just pre-boiling, cook them up in a pot of beer and onions to infuse them with flavor before throwing them on the grill for a final browning. Two cans of beer, a half an onion and about another 1-2 cups of water will cook up ten brats in 30 minutes on a gentle simmer. Then you'll know they are done inside when they come off the grill, and you can't beat the flavor!
