Combine gravy mix and water in 2-cup glass measure.
Cook at HIGH 2 1/2 to 3 minutes, or until thickened; stir twice.
Arrange turkey in four piles (to fit bread) in 8-inch square dish.
Cook, covered with plastic wrap, at MEDIUM-HIGH 1 1/2 to 2 minutes, or until heated through.
Arrange turkey on bread; top with gravy.