HEAT oven 350ºF.
CUT half the onion into thin slices; place in large bowl. Add cabbages; mix lightly. Mix dressing and 2 Tbsp. barbecue sauce. Add to cabbage mixture; toss to coat. Refrigerate until ready to use.
HEAT oil in large skillet. Add meat; cook 5 min. or until browned on both sides, turning after 3 min. Transfer to 13x9-inch baking dish. Chop remaining onion piece; sprinkle over meat. Mix broth, 1/2 cup of the remaining barbecue sauce and garlic; pour over meat. Cover.
BAKE 2-1/2 to 3 hours or until meat is done (160ºF). Let stand, covered, 10 min. Shred meat; place in large bowl. Add remaining barbecue sauce; toss to coat.
FILL each roll with 1/2 cup meat mixture and 1/3 cup coleslaw just before serving.