Preheat oven to 350 degrees
Heat olive oil in a large, heavy-based skillet (e.g., cast iron) over medium-high heat. Remove chicken from marinade, shaking off any excess (reserve marinade). Add chicken to the skillet and cook until it begins to brown; repeat with other side. Remove the seared chicken and set aside.
Remove any black bits from the skillet, then add the rice, chicken stock, water, oregano, salt and pepper, and leftover marinade. Let the rice mixture come to a simmer.
Cover the rice and place in the oven. Bake for a total of 35 minutes; when there are 15 minutes left, place the chicken thighs on the rice. Cover again and bake for the remaining 15 minutes.
When the chicken and rice have cooked for the full 35 minutes, uncover and bake for an additional 10 minutes, or until the liquid is absorbed.
Remove from the oven and let rest for 5-10 minutes. Garnish with fresh parsley and lemon slices.