Whisk together olive oil, lemon juice, minced garlic, oregano, salt, and pepper in a bowl to create the marinade.
Toss the chicken cubes in the marinade and allow to sit for 15 minutes.
Sauté the chicken in a large skillet over medium-high heat until the internal temperature reaches 165°F (74°C), approximately 8 to 10 minutes.
Distribute the cooked quinoa evenly across five bowls.
Top each bowl with equal portions of the cooked chicken, cucumber, cherry tomatoes, red onion, and olives.
Finish each bowl with a sprinkle of feta cheese and a dollop of tzatziki sauce.