In a large bowl, whisk together olive oil, lemon juice, garlic, oregano, salt, and pepper to create the marinade.
Add cubed chicken to the marinade, toss to coat, and refrigerate for 15 minutes.
Rinse quinoa under cold water and combine with chicken broth in a saucepan; bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes.
Heat a large skillet over medium-high heat and cook the marinated chicken until the internal temperature reaches 165°F (74°C), approximately 8 to 10 minutes.
Fluff the cooked quinoa with a fork and divide evenly among four meal prep containers.
Top each portion of quinoa with equal amounts of cooked chicken, tomatoes, cucumber, red onion, olives, and feta cheese.
Garnish with fresh parsley and serve with a side of tzatziki sauce.