Place the quinoa in a fine-mesh strainer and rinse thoroughly under cold running water for about 30 seconds.
Bring to a boil, then reduce the heat to low and cover. Simmer for approximately 15 minutes, or until the liquid has been absorbed and the quinoa grains have opened.
Fluff the quinoa gently with a fork and spread it onto a large plate or baking sheet.
Allow it to cool to room temperature.
While the quinoa cools, chop the cucumber, tomatoes, red onion, parsley, dill, mint, and roasted red peppers.
Whisk together the olive oil, lemon juice, lemon zest, red wine vinegar, garlic, oregano, Dijon mustard, salt, and black pepper.
Add the Kalamata olives, feta cheese, and fresh herbs. Pour the dressing over everything and gently toss until evenly combined.
Before serving, toss gently again and add a little extra lemon juice, olive oil, feta, or fresh herbs if desired.
For the best flavor, refrigerate the salad for 20–30 minutes before serving.