Place scrubbed potatoes with skins in oven at 375 degrees. Bake for 45 minutes or until done. After potatoes are baked, slice them 1 1/2 inches thick. Place sliced potatoes around freshly cleaned chickens in a large baking pan. Sprinkle chickens and potatoes with olive oil, salt and pepper, fresh oregano, and lemon juice. Place chunks of butter inside chickens and onto potatoes. Also place a lemon wedge freshly squeezed inside each chicken. Place inside oven at 325 degrees. Baste chicken and potatoes with juices from the pan for added moisture. Chickens will be done when skins are crispy brown and legs lift easily from the joint. Serve the meal with fresh Greek bread, slightly toasted, to dip into the juices.