In a saucepan bring about 1 inch water to boiling. Add asparagus, sweet pepper strips, and onion. Return just to boiling; reduce heat slightly. Boil, covered, about 1 minute or until crisp-tender. Drain well; set aside a few asparagus tips for garnish. Spread the asparagus-pepper mixture evenly in prepared baking dish. Layer with zucchini slices.
In a large bowl combine eggs, half-and-half, parsley, salt, and black pepper. Pour over vegetables in baking dish. Sprinkle with cheese. Bake about 35 minutes or until a knife inserted near center comes out clean. Let stand for 10 minutes before serving. Garnish with the reserved asparagus tips.