Slice one onion and put half in bottom of crock-pot. Add meat and all other ingredients with remaining half of onion on top. Cover and cook 8 to 12 hours on low. Remove bone and fat from meat. Cut meat in chunks and put back in crock-pot. Cover with remaining 1/2 chopped onion and 16 ounce barbecue sauce. Cover and cook 2 or 3 hours on high or 4 to 6 hours on low, stirring occasionally. Serve on large hamburger buns.