1. Preheat oven to 450'F. Arrange fillets in 8x8x2" square baking dish.
2. Saute onion and garlic in oil in medium-size skillet over medium heat 3-5 minutes or until lightly softened. Add tomatoes, capers, basil, olives, lemon juice, oregano, salt if using, and pepper. Simmer, stirring occasionally, 8 minutes. Spoon sauce over fish.
3. Bake in preheated 450'F. oven for 10 minutes or until cooked through.