Step 1. Preheat the oven to 180°C. Spread the potato and onion evenly in a large baking dish. Drizzle half the olive oil evenly over the vegetables and bake for 15 minutes.
Step 2. Toss through the zucchini and bake for 15 minutes or until the potato is turning golden and almost cooked.
Step 3. Place the fish fillets on top of the vegetables. Scatter the tomatoes, olives and capers around the fish. Drizzle the remaining olive oil evenly over the top. Return to the oven and bake for 15 minutes or until the fish is cooked through and the vegetables are tender.
Step 4. Scatter the herbs on top and serve with wedges of lemon and a side of green salad.