Rinse the quinoa thoroughly under cold water. Combine quinoa and water in a saucepan and bring to a boil.

Reduce heat, cover, and simmer for 15 minutes, or until all water is absorbed. Fluff with a fork and let cool.

In a large bowl, combine the cooked and cooled quinoa with the diced cucumber, halved cherry tomatoes, sliced red onion, diced bell pepper, and chopped fresh parsley. Whisk together the olive oil, lemon juice, salt, and black pepper for the dressing. Pour the dressing over the quinoa and vegetables, then toss to combine.