Trim brisket well, and then combine the brown sugar, seasoned salt, chili powder, and black pepper to make a dry rub. Coat the brisket well, and allow it to reach room temperature. Hethe at grill to around 325 degrees. Place brisket on the grill and cook on each side for approximately 30 minutes. Remove brisket from the grill.
Heat oven to 275 degrees, and wrap brisket in foil. You can add sliced onions and garlic cloves to the brisket before wrapping with foil if you like. Place foil-wrapped brisket in a baking dish, and bake brisket for an additional 3 hours. Remove brisket and allow to rest for 20 minutes before slicing.