In a medium bowl, whisk together the olive oil, lemon juice, minced garlic, and dried oregano.
Add the cubed chicken to the marinade and toss to coat; marinate for at least 15 minutes.
While the chicken marinates, prepare the quinoa and chop the fresh vegetables.
Heat a large skillet over medium-high heat and cook the chicken until golden brown and the internal temperature reaches 165 degrees Fahrenheit, approximately 8 to 10 minutes.
Divide the cooked quinoa evenly among four bowls.
Top the quinoa with the cooked chicken, diced cucumber, halved tomatoes, sliced red onion, and olives.
Garnish each bowl with crumbled feta cheese.
Serve each bowl with a dollop of tzatziki and hummus.