In a medium saucepan, bring 2 cups of water or vegetable broth to a boil. Add the rinsed quinoa, reduce heat to low, cover, and simmer for 12-15 minutes until the quinoa is tender and the liquid is absorbed. Fluff with a fork and let it cool slightly.
While the quinoa cooks, prepare the vegetables: Halve the cherry tomatoes, dice the cucumber, finely chop the red onion, and halve the Kalamata olives. Set aside.
In a small bowl or jar, whisk together the dressing ingredients: olive oil, lemon juice, minced garlic, dried oregano, salt, and black pepper. Adjust seasoning to taste.
In a large mixing bowl, combine the cooked quinoa, cherry tomatoes, cucumber, red onion, Kalamata olives, and crumbled feta cheese. If using chickpeas or grilled chicken, add them now.
Pour the dressing over the quinoa mixture and toss gently to coat all the ingredients evenly. Sprinkle the chopped fresh parsley over the top and mix lightly.
Divide the mixture into 4 bowls or serve family-style in a large bowl. Enjoy your Mediterranean quinoa bowl warm or chilled, perfect for a healthy lunch or dinner!