HEAT oven to 375°F. Mix meat, stuffing mix, 1 cup water and onions until well blended. Shape into 6 (1/2-inch-thick) oval patties. Place in 15x10x3/4-inch pan.

BAKE 25 min. or until patties are done (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 water; simmer on low heat 1 to 2 min. or until sauce is heated through. Serve over meat patties.