1. Cook quinoa: In a saucepan, bring 2 cups of water to a boil. Add quinoa, reduce heat to low, cover, and simmer for 15 minutes. Remove from heat and let it sit for 5 minutes, then fluff with a fork.
2. Cook lentils: In another saucepan, bring 2 cups of water to a boil. Add lentils, reduce heat to low, cover, and simmer for 20 minutes or until tender. Drain any excess water.
3. Prepare vegetables: While quinoa and lentils are cooking, chop the cherry tomatoes, cucumber, red onion, and parsley.
4. Combine ingredients: In a large mixing bowl, combine cooked quinoa, lentils, cherry tomatoes, cucumber, red onion, and parsley.
5. Make dressing: In a small bowl, whisk together olive oil, lemon juice, salt, and black pepper.
6. Toss salad: Pour dressing over the salad and toss to combine. Adjust seasoning if needed. Serve chilled or at room temperature.