Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with cooking spray or a little olive oil.
In a large bowl, combine the sliced zucchini, diced onion, diced red bell pepper, minced garlic, halved cherry tomatoes, oregano, basil, salt, and black pepper. Drizzle with olive oil and toss until well coated.
Spread the vegetable mixture evenly in the prepared baking dish.
Sprinkle the shredded mozzarella cheese and grated Parmesan cheese evenly over the top of the vegetables.
Bake in the preheated oven for 25-30 minutes, or until the vegetables are tender and the cheese is bubbly and golden brown.
Remove from the oven and let it cool for a few minutes. Garnish with chopped fresh parsley before serving.