Preheat your oven to 375°F (190°C). Lightly oil a baking dish.
Spread zucchini slices in an even layer, followed by tomato slices and corn.
Scatter the onion and garlic evenly over the vegetables.
Drizzle with olive oil, sprinkle oregano, salt, and pepper.
Top with Parmesan cheese and breadcrumbs if using.
Bake uncovered for 30–35 minutes, until the cheese forms a golden crust.
Garnish with fresh basil leaves and serve warm.