Combine first 3 ingredients in a Dutch oven. Add beef; bring to a boil. Cover, reduce heat, and simmer 3 hours or until very tender, turning beef occasionally. Remove beef from pan. Reserve 2 cups cooking liquid; discard remaining cooking liquid. Shred beef with 2 forks. Return shredded beef to pan. Add reserved cooking liquid, barbecue sauce, and cranberry sauce; stir well. Cook over medium-low heat 10 minutes or until thoroughly heated. Serve beef mixture on buns.