Rinse quinoa thoroughly under cold water, then combine with water in a saucepan and bring to a boil.

Reduce heat to low, cover, and simmer for 15 minutes, or until all water is absorbed; let it cool completely after cooking.

In a large bowl, combine the cooled quinoa with diced cucumber, halved cherry tomatoes, finely chopped red onion, crumbled feta cheese, and fresh parsley.

Whisk together olive oil, lemon juice, salt, and black pepper in a small bowl, then pour the dressing over the salad and toss to combine before serving.