Heat oven to 400. Grease pie plate, 10 x 1 1/2 inches. Sprinkle ham, cheese and onions in plate. Beat remaining ingredients until smooth. Pour into plate. Bake until golden brown and knife inserted in center comes out clean, 35 to 40 minutes. Cool 5 minutes.
1 1/2 times the recipe fits in 9 x 13 inch pan.