In a large bowl, combine the chopped romaine lettuce, cherry tomatoes, cucumber, bell pepper, red onion, Kalamata olives, mozzarella balls, and fresh basil.
In a small bowl, whisk together the olive oil, red wine vinegar, dried oregano, salt, and pepper until well combined.
Pour the dressing over the salad mixture and toss gently to combine, ensuring all ingredients are evenly coated.
Let the salad sit for about 10 minutes to allow the flavors to meld before serving.
Serve chilled or at room temperature.