In 3 1/2- to 4-quart slow cooker, arrange beef. Add remaining ingredients except buns; mix well.
Cover; cook on High heat setting 5 to 6 hours.
Remove beef from slow cooker; place on cutting board. Shred beef with 2 forks; return to slow cooker, and mix well. Cover; cook about 20 minutes longer or until beef is moistened and hot.
To serve, with slotted spoon, spoon about 1/3 cup beef mixture into each bun. Mixture can be kept warm for several hours on Low heat setting.