Preheat oven to 350°F. Place ribs on a rimmed baking sheet. Generously rub spice mix over both sides of ribs. Wrap tightly in foil.
Bake for 45 minutes. Then reduce oven temperature to 275°F and continue baking for 1 3/4 to 2 1/2 hours, or until meat is very tender and pulling away from bones.
Preheat grill to medium-high heat. Carefully unwrap ribs and place directly on the grill. Baste with barbecue sauce, turning occasionally, until sticky and caramelized—about 5 to 8 minutes.
Transfer to a cutting board. Slice between bones and serve with extra barbecue sauce if desired.