Rinse quinoa under cold water. In a medium saucepan, bring 2 cups of water to a boil. Add quinoa, reduce heat to low, cover, and simmer for 15 minutes until tender. Fluff with a fork and let cool.

Dice cucumber, halve cherry tomatoes, finely chop red onion and parsley, and slice olives. Place all in a large mixing bowl.

In a small bowl, whisk together olive oil, lemon juice, salt, and pepper until well combined.

Add cooled quinoa and feta cheese to the vegetables. Pour dressing over and toss gently to combine.