In a microwave-safe bowl, combine the beer, butter, 1 tablespoon garlic powder and seasoned pepper. Heat in the microwave for 2 minutes, or until butter is melted and mixture is hot. Set aside.
Season chicken generously with the garlic powder, ground black pepper and seasoned salt to taste.
Brush the grilling surface with oil. Place chicken onto the grill bone side down. Close the lid, and cook for about 45 minutes, or until the chicken skin is starting to blister.
Turn the chicken over, so it is bone side up. They will be black and charred, but the chicken meat will be fine. Pierce the membrane of the bone with a fork, and ladle some of the beer mixture into the 'cup' formed by the bones. Throw a teaspoon or so of garlic powder on the coals, close the lid, and seal the vents.
Repeat ladling the beer mixture into the chicken, and throwing garlic powder onto the coals every 5 minutes, until the mixture is gone. The chicken should be tender and juices should run clear.