In a large bowl, combine the mixed salad greens, cherry tomatoes, cucumber, bell pepper, red onion, shredded carrots, and olives if using. Toss gently to mix the vegetables evenly.
In a small bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, salt, and pepper until well combined.
Drizzle the dressing over the salad and toss gently to coat all the ingredients.
If using, sprinkle the crumbled feta cheese on top of the salad before serving.
Serve immediately or chill in the refrigerator for about 15-30 minutes to enhance the flavors.