1. Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish with olive oil.
2. In a large bowl, combine the zucchini, summer squash, onion, garlic, cherry tomatoes, and basil. Drizzle with olive oil and season with salt, pepper, and oregano. Toss until well coated.
3. Layer half of the vegetable mixture in the prepared baking dish. Sprinkle half of the Parmesan and mozzarella cheese over the vegetables.
4. Add the remaining vegetable mixture on top and sprinkle with the remaining cheeses. If using, evenly distribute the breadcrumbs over the top for an added crunch.
5. Cover the dish with foil and bake for 25 minutes. Then, remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and golden brown.
6. Let the casserole cool for a few minutes before serving. Garnish with additional basil if desired.

Remember the times when my daughters, Olivia and Isabella, would sit on the kitchen counter watching me cook? This is the perfect dish to involve little hands in the kitchen. They love arranging the vegetables in the dish and sprinkling on the cheese.