In large bowl, mix potatoes, mushrooms, carrots and onions. Crumble beef over vegetables. Add barbecue sauce; toss until well coated. Spoon 1/4 of mixture onto each sheet of foil. On each sheet, bring up 2 sides of foil so edges meet. Seal edges, making tight 1/2-inch fold; fold again, allowing space for heat circulation and expansion. Fold other sides to seal.