In a large stockpot, place both racks of ribs; add enough water to cover ribs. Add marinade, bay leaves and onion. Bring mixture to a boil over high heat. (This will create foam on top.) Reduce to medium-low heat; simmer 45 minutes or until ribs are just tender. Remove ribs from cooking liquid; drain on rimmed baking sheet. Heat grill to medium heat (about 350 degrees F.). Meanwhile, in a small mixing bowl, stir together the barbecue sauce and brown sugar. Brush over both sides of ribs. Place ribs on grill, bone side down, close lid. Grill for 7 minutes, turn and grill 7 minutes more.