Prepare the vegetables In a baking dish, add diced zucchini, chopped onion, cherry tomatoes, and olives. Drizzle with olive oil, season with salt, pepper, oregano, and garlic. Toss to coat evenly.
Add the fish Place the fish fillets on top of the vegetables. Drizzle with lemon juice and a little more olive oil. Sprinkle with thyme or rosemary and chili flakes if using.
Bake Bake uncovered for 20–25 minutes, or until the fish is cooked through and flakes easily with a fork. The vegetables should be tender and slightly caramelized.
Garnish and serve Sprinkle with fresh parsley and serve hot with crusty bread or rice.