1. To make dressing, combine oil, vinegar, tomato sauce, and oregano in a small bowl; whisk to blend. Season with salt and pepper if desired. Set aside.
2. Combine arugula, romaine, basil, tomatoes, bell pepper, onion, mushrooms, and dressing in a large serving bowl; toss gently to blend.
3. Top with bocconcini and crushed red pepper (if desired); serve immediately.