Rinse quinoa, then cook it in salted boiling water for 12 minutes. Rest covered off heat for 5 minutes, then fluff and spread to cool.

While quinoa cooks, halve the tomatoes, dice the cucumber, thinly slice the red onion, and halve the olives.

Whisk together olive oil, lemon juice, oregano, and salt to make the dressing.

Toss warm quinoa with most of the dressing, then fold in the tomatoes, cucumber, onion, and olives.

Crumble feta over the bowl, scatter parsley, and serve right away.