Bring to a boil, reduce heat, and simmer until brats are cooked through (about 10 to 12 minutes). Remove brats and continue cooking onions in beer while grilling the brats.
Add brats to grill on medium heat, turning frequently, until browned, about 5 minutes.
Grill the boiled onions until golden brown.
Remove brats from the grill and place them in the buns. Serve with your choice of toppings & sauce.