Place a roasting pan over 2 burners on medium-high heat.
Add enough olive oil to just coat the bottom.
Slice the onions and peppers thinly.
Sauté the onions and peppers in the pan until they soften and have a bit of brown color.
Season with salt and pepper.
Remove these to a heatproof bowl and cover with foil.
Place the brats in a single layer in the warm roasting pan.
Pour the beer over the brats.
As soon as it comes to a very gentle boil, lower the heat so it stays at a low simmer.
Cover the pan with aluminum foil.
Simmer the brats for approximately 20 minutes until the juices are bubbling inside the casings.
Depending on the size of your roasting pan, you may have to add more beer.
While the brats are simmering, set up your grill. Fill a charcoal chimney with briquettes.
Place a loose wad of newspaper in the bottom of the chimney.
Light the paper and allow the briquettes to become white with a red hot interior.
When the coals are hot, empty them into the grill base and spread them evenly.
Place the grill grate over the coals and wipe it down with a wad of paper towel that has been dipped in vegetable oil.
Use your tongs for this.
Using tongs, remove the brats from the beer bath to a large platter or baking dish.
Leave the beer simmering.
Place the bratwursts over the coals and grill for approximately 5 minutes, turning a couple of times to char all sides.
While the brats are grilling, place the sauerkraut in the simmering beer just to warm it up.
Remove this to a heatproof serving bowl and cover with foil.
When the brats are cooked through, remove them to the beer bath to keep them warm.
You can serve them right out of the pan.
Serve the brats with the rolls, onions and peppers, mustard, and sauerkraut.
You might also want to serve a nice German style potato salad with a bacon vinaigrette.