Wash the baby potatoes thoroughly.
Place the potatoes in a large pot of salted water and bring to a boil.
Cook until tender, about 15-20 minutes.
Drain the potatoes and let them cool slightly.
Cut the potatoes in half or quarters.
In a large bowl, combine potatoes, cherry tomatoes, cucumber, and red onion.
Whisk together olive oil, lemon juice, salt, and pepper in a separate bowl.
Pour the dressing over the salad and toss gently.
Add chopped parsley and mix well.
Serve chilled or at room temperature, garnishing with feta cheese if desired.