Trim the brisket well to remove large excess fat and any silver skin. Pat the meat dry with paper towels.
In a bowl, combine 1/2 cup brown sugar, 2 tablespoons seasoned salt, 1 tablespoon chili powder, and 2 teaspoons black pepper; mix until evenly blended.
Rub the dry mixture all over the brisket, pressing it into the surface so the meat is well coated. Let the rubbed brisket sit at room temperature for about 30–60 minutes.
Heat a grill to around 325°F (163°C). Place the brisket on the grill and cook for approximately 30 minutes on one side, then flip and cook about 30 minutes on the other side, until the exterior is browned.
Remove the brisket from the grill. Preheat the oven to 275°F (135°C) if it is not already heated.
Wrap the brisket tightly in aluminum foil and place the foil-wrapped brisket in a baking dish or roasting pan.
Bake the foil-wrapped brisket in the oven for about 3 hours, or until an instant-read thermometer inserted into the thickest part reads about 195°F (90°C).
Carefully open the foil and return the brisket to the oven (uncovered). Cook for another hour or until the internal temperature reaches 200–202°F (93–94°C).
Remove the brisket from the oven, loosely tent with foil, and let it rest for 30 minutes before slicing against the grain.