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 mixing bowl, combine cooked quinoa, cherry tomatoes, cucumber, and feta cheese.
5. In a small bowl, whisk together olive oil, lemon juice, salt, and black pepper.
6. Pour the dressing over the quinoa mixture and toss to combine.
7. Serve immediately or refrigerate for later.