HEAT grill to medium heat.
MIX first 4 ingredients until blended. Place meat in disposable foil pan; cover with barbecue sauce mixture. Refrigerate 20 min., turning after 10 min.
PLACE pan on grill grate; cover with lid of grill. Cook 3 to 3-1/2 hours or until meat is tender. Remove from grill; cover with foil. Let stand 10 min.
SHRED meat with 2 forks; mix with steak sauce. Serve in buns.