Rinse the quinoa thoroughly under cold water to eliminate any bitterness, then cook it with 2 cups of water according to package instructions until fluffy. Set aside.

Preheat your oven to 425°F (220°C).

In a large mixing bowl, combine the zucchini, yellow squash, red bell pepper, red onion, and cherry tomatoes.

Drizzle the vegetables with olive oil, and add the minced garlic, dried oregano, salt, and black pepper. Toss well until all vegetables are evenly coated.

Spread the seasoned vegetables onto a baking sheet in a single layer. Roast in the preheated oven for 20 to 25 minutes, stirring halfway through, until the vegetables are tender and lightly caramelized.

Once the quinoa is cooked, fluff it with a fork and transfer it to a large serving bowl.

Add the roasted vegetables and any pan juices to the bowl with quinoa.

Pour in the lemon juice and add the chopped parsley, tossing gently to combine.

Finally, fold in the crumbled feta cheese and sliced kalamata olives just before serving.

Serve warm, at room temperature, or chilled.