In a mixing bowl, whisk together olive oil, lemon juice, garlic, oregano, salt, and pepper. Add chicken breasts and marinate for 30 minutes.

Rinse quinoa under cold water. Combine quinoa, broth, olive oil, and salt in a saucepan. Bring to boil, then cover and simmer for 15 minutes.

Preheat grill. Grill marinated chicken for 6-7 minutes on each side until cooked through. Let rest before slicing.

Assemble bowls with quinoa base, sliced chicken, cherry tomatoes, cucumber, red onion, olives, feta cheese, and parsley.

Drizzle with extra olive oil and a squeeze of lemon juice before serving.