Country Salisbury Steak

1-1/2 lb. extra lean ground beef
1 pkg. (6 oz.) STOVE TOP Stuffing Mix for Chicken
1-1/2 cups water, divided
3/4 cup chopped onions
1 pkg. (8 oz.) fresh mushrooms, sliced
1/2 cup KRAFT Original Barbecue Sauce

PREHEAT oven to 375°F. Mix meat, stuffing mix, 1-1/4 cups of the water and the onions until well blended. Shape into six 1/2-inch-thick oval patties. Place on 15x10x1-inch baking pan.
BAKE 25 min. or until cooked through (160°F).

MEANWHILE, spray large nonstick skillet with cooking spray. Add mushrooms; cook on medium-high heat 5 min. or until lightly browned, stirring occasionally. Add barbecue sauce and remaining 1/4 cup water. Reduce heat to low. Cook 1 to 2 min. or until sauce is heated through. Serve over the patties.