Place oven rack in lower half of oven; heat oven to 350°F. Arrange opened cooking bag in 13x9-inch pan. Place ribs in bag with seasoning; shake to coat. Arrange ribs in single layer in bag, meaty side up. Pour water over ribs. Close bag loosely with nylon tie provided with cooking bag. Cut 4 small holes in bag to allow steam to escape.
Bake in lower half of oven at 350°F. for 45 minutes. Meanwhile, heat grill.
When ready to grill, carefully open bag. Remove ribs from bag; place on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Brush ribs with barbecue sauce; cook 20 minutes, turning and brushing occasionally with sauce.