Beef Stroganoff

2 lbs stew beef, cut into 1 inch cubes
8 oz pkg mushrooms, halved or sliced
1/2 cup chopped onion
1 pkg McCormick Slow cookers Beef Straganoff Seasoning
1 cup water
1 cup sour cream

Place beef, mushrooms and onion in slow cooker. Mix seasoning and water until blended. Pour over beef and vegetables; toss to coat well. Cover. Cook 8 hours on low or 4 hours on high. Stir in sour cream until well blended. Cover. Cook 10 min longer on low. Serve over noodles or rice, if desired