1. Rinse the quinoa under cold water.
2. In a saucepan, bring the water to a boil. Add the quinoa, reduce heat, cover, and simmer for 15 minutes or until water is absorbed.
3. Remove from heat and let it sit, covered, for 5 minutes. Fluff with a fork.
4. In a large mixing bowl, combine the cooked quinoa, chicken, cherry tomatoes, cucumber, red onion, and feta cheese.
5. In a small bowl, whisk together the 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.