In a small bowl, stir together olive oil, vinegar, garlic, oregano, red-pepper flakes, salt and pepper to taste and ¼ cup of chopped fresh basil. Pour mixture over tomatoes, mozzarella, red onions and olives.
¼ cup extra-virgin olive oil, 2 Tablespoons red wine vinegar, 2 large garlic cloves, ½ cup fresh basil leaves, divided, ¼ teaspoon dried oregano, kosher salt, fresh ground pepper, ¼ teaspoon red pepper flakes