Pierce bratwurst all over with a fork.

In a medium pot, combine the bratwurst, beer, and half of the onions. Bring to a simmer over medium-high heat.

Simmer for 15 minutes or until the brats are firm and cooked through

Transfer the brats to a plate and reserve some of the cooking liquid.

Meanwhile, in a large skillet, heat the oil over medium-high heat.

Add the remaining onions and sliced bell peppers and cook for 15 minutes, or until they are very soft, tossing occasionally.

Add the bratwurst in the last 5 minutes to lightly brown. If the vegetables begin to get too dark add some of the reserved cooking liquid.

Salt and pepper to taste.

To serve spread mustard on the bun or hoagie roll, insert a bratwurst and top with onions and peppers.

Enjoy!!!