Preheat your grill to 275°F (135°C).
Mix brown sugar, paprika, salt, black pepper, garlic powder, and onion powder in a bowl.
Rub the spice mixture all over the ribs.
Wrap the ribs in aluminum foil and place them on a baking sheet.
Cook the ribs on the grill for 2 hours.
Remove the ribs from the grill, unwrap them, and brush with barbecue sauce.
Place the ribs back on the grill for an additional 10 minutes, uncovered.
Remove from the grill, let rest for 10 minutes, then serve.