Rinse the quinoa under cold water using a strainer to remove any bitterness.
In a pot, combine the rinsed quinoa and 2 cups of water. Bring to a boil over medium-high heat.
Once boiling, reduce the heat to low, cover, and let it simmer for about 15 minutes or until all the water is absorbed. Remove from heat and let it sit, covered, for an additional 5 minutes.
Fluff the quinoa with a fork and allow it to cool for a few minutes.
In a large mixing bowl, combine the cucumber, bell pepper, cherry tomatoes, red onion, olives, feta cheese, and parsley.
In a small bowl, whisk together the olive oil, lemon juice, dried oregano, salt, and pepper.
Add the cooled quinoa to the vegetable mixture and pour the dressing over the top. Toss everything together until well combined.
Taste and adjust seasoning if necessary. Serve chilled or at room temperature.