Marinate the chicken breast with olive oil, lemon juice, oregano, garlic powder, salt, and black pepper. Let it sit for at least 15 minutes.

Cook the marinated chicken in a skillet over medium heat for about 20 minutes or until fully cooked, then slice it.

In a bowl, combine quinoa, diced cucumber, cherry tomatoes, red onion, feta cheese, and kalamata olives.

For the tzatziki sauce, mix Greek yogurt, grated cucumber, minced garlic, lemon juice, dill, and salt in a separate bowl.

To serve, place the quinoa mixture in a bowl, top with sliced chicken, and drizzle with tzatziki sauce.