Trim fat from brisket. Place brisket in a large roasting pan; top with onion. Combine chili sauce, beer, sugar, and Worcestershire sauce; pour over onion. Cover and bake at 325° for 1 1/2 hours.
Stir onion into cooking liquid. Arrange the carrots and potatoes around brisket; spoon cooking liquid over vegetables. Sprinkle seasoned salt and garlic pepper over meat and vegetables. Cover and bake an additional 1 1/2 hours or until vegetables are tender.
Cut brisket diagonally across the grain into thin slices. Arrange the beef and vegetables in each of 8 shallow bowls, and serve with sauce.
Note: If you don't have a large roasting pan, cut brisket in half, and place in a large Dutch oven.
I've made this a couple times, once with brisket and once with chuck roast. I preferred with the chuck because the brisket was so fatty and greasy in spite of trying to trim a lot of the fat off. I brown the meat in the dutch oven prior to cooking though the instructions don't mention that. And just because I prefer them over potatoes, I used carrots, rutabagas and parsnips. This is a really easy and tasty dish.
Made this for Hannukah dinner and it was a big hit with the family. The only downside for me was the fact that the potatoes were competing with the latkes and it ended up being potato overload. Will definitely make again.