Preheat oven to 375 degrees F.
Arrange the bread slices in a single layer on a baking sheet. In a bowl, mix the onion, garlic, 2 tablespoons olive oil, oregano, basil, and parsley. Gently toss in the tomatoes. Top bread slices with the tomato mixture. Sprinkle with feta cheese and Parmesan cheese. Drizzle with remaining olive oil.
Bake 10 minutes in the preheated oven, or until cheese is melted and bread is lightly toasted.