In a medium mixing bowl, whisk together olive oil, lemon juice, minced garlic, oregano, salt, and pepper to create the marinade.
Add the cubed chicken to the marinade, ensuring all pieces are well coated, and let sit for at least 15 minutes.
Place a large skillet over medium-high heat and add the marinated chicken in a single layer.
Cook the chicken for 8 to 10 minutes, turning occasionally, until the exterior is browned and the internal temperature reaches 165 degrees Fahrenheit.
Divide the cooked rice equally among four serving bowls.
Arrange the cooked chicken, tomatoes, cucumber, red onion, and olives over the rice base.
Garnish each bowl with crumbled feta cheese and a dollop of tzatziki sauce before serving.