Preheat oven to 350.  Drizzle olive oil on a 9x13 pan.  Place sliced onion and 1 sliced tomato on top of the pan.  Place chicken on top of onion and tomato.  Sprinkle olive oil, black pepper, salt, and oregano over top. Place the rest of the tomato slices on top of chicken and put 3-4 bay leaves between the chickens. Bake covered for 1/2 an hour then uncovered for another 1/2 an hour or until fully cooked. Serve chicken with tomatoes and it tastes delicious.