HEAT oven to 375°F. Mix meat, stuffing mix, 1 cup of the water and the onions until well blended. Shape into six 1/2-inch-thick oval patties. Place in 15x10x3/4-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; simmer 1 to 2 min. or until sauce is heated through. Serve over the patties.