A lot goes into the cooking..... I'll do the short version here again.
Grill 1/2 way done first, putting on the grill marks and browning.
Now, put in an empty coffee can with your onions or other spices. Fill
with beer and simmer. If you do it the other way, they dry out. If you
simmer 2nd, you can pull a brat out of that hot beer hours later and
it'll be juicy and tasty.