In a bowl whisk together the oil, lemon juice, oregano, garlic and salt and pepper. In a shallow dish coat the fish steaks with the mixture and let marinate, covered and chilled, for 15 minutes. Arrange the fish in a foil lined baking pan and bake for 12 to 15 minutes or until fish is just cooked. In a bowl toss the tomatoes with the basil and salt and pepper to taste. Transfer the fish to serving plates and top each with some of the tomato/basil salad. Sprinkle with lemon juice and garnish with lemon wedges.