1. HEAT oven to 350 degrees F.
2. CUT two 1/2-inch thick rounds horizontally from center of bread, reserving remaining bread for another use. Brush bread rounds on both sides with olive oil. Place on baking sheet. Bake until crisp, about 8 to 10 minutes. Cool 5 minutes.
3. COMBINE oregano, red pepper flakes and mozzarella cheese. Reserve 1/2 cup of cheese mixture. Divide remaining seasoned cheese evenly on top of toasted bread rounds. Sprinkle each with tomatoes, olives and feta cheese. Top with remaining seasoned cheese.
4. RETURN to oven. Bake 12 to 15 minutes or until cheeses melt and crusts are crisp.