1. Preheat your oven to 300°F (150°C).
2. Mix brown sugar, paprika, salt, black pepper, garlic powder, and onion powder in a bowl.
3. Rub the spice mixture all over the ribs.
4. Wrap the ribs in aluminum foil and place them on a baking sheet.
5. Bake in the preheated oven for 2.5 hours.
6. Preheat your grill to medium-high heat.
7. Remove the ribs from the oven and unwrap them.
8. Brush the ribs with barbecue sauce.
9. Grill the ribs for about 10-15 minutes, basting with more sauce and turning occasionally.
10. Remove from the grill and let rest for a few minutes before serving.