Rinse the quinoa under cold water. In a medium pot, bring the vegetable broth to a boil, add quinoa, cover, and reduce heat. Simmer for 15 minutes or until cooked. Fluff with a fork and set aside to cool.

While the quinoa cooks, heat 2 tablespoons olive oil in a large skillet over medium heat. Add the mushrooms and sauté for 5–7 minutes until tender and browned. Add the onion and garlic, and cook for another 3–4 minutes until fragrant.

In a small bowl, whisk together lemon juice, olive oil, salt, and pepper.

In a large bowl, combine the cooked quinoa, sautéed mushrooms, and fresh parsley. Drizzle with lemon dressing, toss gently, and top with feta cheese if desired.

Serve warm or cold, as desired.