Preheat oven to 325 degrees F. In a large saucepan cook onion in hot oil over medium heat about 5 minutes or until tender, stirring occasionally. Reduce heat to low. Add cream cheese. Stir in egg. Stir in corn, zucchini, tomato, bread crumbs, and snipped basil. Transfer to a 2-quart baking dish.
Bake, uncovered, about 50 minutes or until center appears set. Sprinkle with mozzarella cheese. Let stand for 10 minutes before serving. If desired, sprinkle with shredded basil just before serving. Makes 10 (1/2 cup each) servings