Combine chicken, lemon zest, lemon juice, garlic, oregano, and salt in a ziplock bag or bowl. Marinate for at least 20 minutes, preferably overnight.
Preheat oven to 350°F (180°C).
Sear chicken thighs in a large skillet with 1/2 tbsp olive oil until golden brown on both sides. Set aside.
In the same skillet, heat remaining 1 tbsp olive oil and sauté diced onion until translucent. Add rice and stir to coat with the oil.
Pour in chicken stock and water, then add oregano and salt. Bring to a simmer and cook for 30 seconds.
Place seared chicken on top of the rice, cover, and bake in the oven for 35 minutes. Remove the lid and bake for another 10 minutes, until liquid is absorbed and rice is tender.
Let rest for 5-10 minutes before serving, garnished with parsley, oregano, and fresh lemon zest.