Preheat grill over medium-high heat. Clean and oil grate. In a large pot over medium-high heat, add brats, onion, and beer.
Bring to a boil, reduce heat, and simmer until brats are cooked through, about 10 to 12 minutes. Remove brats to a bowl or platter. Continue cooking onions in beer while grilling the brats (use as a topping if desired).
Increase heat to medium and cook brats, turning frequently, until browned, about 5 minutes. Serve in buns with your favorite toppings.
Bratwurst: Always start with raw than pre-cooked sausages. There is nothing wrong with a pack of Johnsonville brats! If you aren't a Wisconsin local but want to pretend you are, you can shop online with Glenn's Market or Usinger's.
Beer: Pilsners and lagers are traditional, but IPAs, porters, and stouts all work wonderfully. If you cannot bear to pour that much beer into a pot for cooking bratwurst, substitute half the beer for water.
Sauerkraut: If you have the time, you can make your own sauerkraut in 5 days with just cabbage, salt, and juniper berries.
Yield: This Wisconsin Beer Brat recipe makes 10 brats. Feel free to halve the recipe if you're serving a smaller crew.
Storage: Refrigerate any extra brats in an airtight container for up to 4 days.
Make ahead: Beer brats are best straight off the grill, but for gatherings with staggered mealtimes, I recommend preparing Wisconsin Beer Brats in a slow cooker so you can keep them warm until you're ready to serve. You'll want to flip-flop the method: Place them in the slow cooker with the onion and beer. Cook for 4 hours on HIGH, or 7 to 8 hours on LOW. Then grill as needed.