1. Preheat your oven to 300°F (150°C).
2. In a small bowl, mix together brown sugar, paprika, garlic powder, onion powder, salt, and black pepper.
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 carefully unwrap them.
8. Brush the ribs with barbecue sauce and grill for 10-15 minutes, turning occasionally and brushing with more sauce.
9. Remove from the grill and let rest for a few minutes before serving.