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

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 and pepper, mustard and 1/2 of cheese. Pour over vegetables. Sprinkle with remaining cheese. Bake in 375 degree oven for 20 minutes or until firm.