1. Prick the brats with a fork in about four different areas. 2. In a large pot combine brats, onion and beer. Bring to a gentle boil over medium high heat and turn the heat down to a simmer. Continue to simmer brats for about 10-15 minutes. Remove from heat. 3. Prepare an outdoor grill for medium high heat. Lightly oil the grate. 4. Remove the brats from the beer onion mixture. Grill the brats for about 5-10 minutes, turning them once. Serve in a bun or sliced with mustard and relish.