1 lg. sweet onion
3 c. thinly sliced zucchini
2 eggs, beaten
1/4 c. butter
1/4 c. milk
1 tsp. salt
1/8 tsp. pepper
1/2 tsp. dry mustard
1 c. grated Swiss cheese

Peel and thinly slice onion, separate into rings, saute onion and zucchini in butter until tender. Place in shallow 1 1/2 quart baking dish. Combine eggs, milk, salt, pepper, mustard and half of cheese. Pour over vegetables. Sprinkle with remaining cheese. Bake at 375 degrees for 20 minutes or until firm.