1. Preheat your grill to medium heat.
2. In a small bowl, mix together brown sugar, paprika, salt, black pepper, garlic powder, and onion powder.
3. Rub the spice mixture all over the ribs.
4. Wrap the ribs in aluminum foil and place them on the grill.
5. Cook for 1.5 hours, turning occasionally.
6. Remove the ribs from the foil and brush with barbecue sauce.
7. Place the ribs back on the grill and cook for another 30 minutes, basting with more sauce as needed.
8. Remove from grill and let rest for 10 minutes before serving.