Cook zucchini and onion in enough salted water to cover, just until slightly tender.
Drain and add next 5 ingredients and mix well. Pour 1/2 into 15x11x2 casserole. Stir margarine into bread crumbs and sprinkle 1/2 on first layer of zucchini mixture.
Repeat layers.
Bake at 350°F for 35 to 45 minutes.
Submitted by: Brenda Z.