In a bowl, combine 1/3 cup gravy, bread crumbs, onion, lemon zest and ginger. Crumble beef over mixture and mix well. Shape into four loaves. Place in an 11x7-in. baking dish.
Bake, uncovered, at 350° for 20 minutes. Drain fat. Arrange potatoes around loaves. Combine remaining gravy with gingersnaps, brown sugar and vinegar. Pour over meat and potatoes. Cover and bake 25-35 minutes longer or until bubbly.