Preheat your oven to 300°F (150°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.
Bake in the preheated oven for 2.5 hours.
Preheat your grill to medium-high heat.
Remove the ribs from the oven and unwrap them.
Brush the ribs with barbecue sauce.
Grill the ribs for 10-15 minutes, basting with more sauce and turning occasionally.
Remove from the grill and let rest for a few minutes before serving.