Rinse quinoa thoroughly then combine it with water or vegetable broth in a saucepan. Bring to a boil, then reduce heat, cover, and simmer for 15 minutes, or until all liquid is absorbed.

While quinoa cooks, whisk together olive oil, lemon juice, Dijon mustard, oregano, salt, and pepper in a small bowl to create the dressing.

Once quinoa is cooked, fluff it with a fork and let it cool slightly. In a large bowl, combine the cooled quinoa, chickpeas, cucumber, cherry tomatoes, red onion, and fresh mint.

Pour the lemon-herb dressing over the quinoa mixture and toss to combine. Garnish with crumbled feta cheese if desired, then serve immediately.