Build a two-zone fire in a charcoal grill using Kingsford® charcoal by situating the coals on only one side of the grill, leaving the other side empty. Preheat the grill to 275°F.
To make the roasted garlic, pull out a length of foil and double it to form a square. Put the garlic and 2 tablespoons of butter on the square. Close the foil in a tight packet. Put the packet over the cool part of the grill and cook over indirect heat for 30 minutes.
Remove the pouch from the grill, open the foil, and let cool slightly. Increase the grill temperature to 500°F. Squeeze the garlic cloves from their skins into a bowl and set aside. Put a cast iron skillet directly over the coals and preheat it. Add the remaining 6 tablespoons butter to the skillet and cook until the butter starts to brown, about 30 seconds. Add the garlic to the butter and cook, stirring, for 30 seconds. Remove the skillet from the grill and set aside.
Meanwhile, put the steaks in a plastic GLAD® food storage bag. Pour the marinade over the steaks and let them stand for 10 minutes. Remove the steaks from the marinade and season them liberally with the rub. Put the steaks on the grill over direct heat and cook for 6–9 minutes total, depending on desired doneness, flipping once.
Remove the steaks from the grill and drizzle with roasted garlic brown butter. Let the steaks rest for 5 minutes before serving.