1. Rinse the quinoa under cold water.
2. In a saucepan, bring water to a boil. Add quinoa, reduce heat to low, cover, and simmer for 15 minutes.
3. Remove from heat and let it sit, covered, for 5 minutes. Fluff with a fork.
4. In a large mixing bowl, combine cooked quinoa, cucumber, red bell pepper, red onion, parsley, and feta cheese.
5. In a small bowl, whisk together olive oil, lemon juice, salt, and black pepper.
6. Pour the dressing over the salad and toss to combine.
7. Serve immediately or refrigerate for later.