Preheat oven to 325°.
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.