In a mixing bowl, combine olive oil, lemon juice, oregano, salt, and pepper. Coat the chicken and marinate for 15-30 minutes.

Bring a pot of water to a boil and add rice. Cook for 15-20 minutes, then fluff and drain.

Heat a skillet over medium-high heat and cook the marinated chicken for 6-8 minutes each side until golden brown and cooked through.

While the chicken rests, mix Greek yogurt, cucumber, garlic, and salt in a bowl to create tzatziki sauce.

Assemble the bowls with rice at the bottom, topped with sliced chicken, tzatziki, and optional toppings.