Wash all vegetables thoroughly under cold running water. Chop the lettuce, cherry tomatoes, cucumber, bell peppers, and red onion into bite-sized pieces.

Combine the chopped vegetables in a large mixing bowl and gently toss them together.

In a separate small bowl, whisk together olive oil and lemon juice until smooth. Add salt and pepper to taste.

Pour the dressing over the salad and toss everything together until the vegetables are evenly coated.

If desired, sprinkle crumbled feta cheese on top before serving, or serve it on the side.