Saute the onion and garlic in olive oil until onions are tender. Add onions to barbeque sauce and stir well.
Place uncooked ham in a baking bag. Pour about 1/2 gallon of barbeque sauce mixture into the bag. Seal the bag and marinate in the refrigerator overnight - about 8 to 12 hours. Remove the ham from the baking bag and place it on the grill. Cook ham until the meat is tender, basting often with barbeque mixture.
Recipe courtesy of Jobbie Toole