Squeeze the juice from 1 lemon. Slice the other one.
Put the chicken and potatoes in a baking pan large enough to hold them in a single layer. Sprinkle the lemon juice, oil, oregano, garlic, and salt and pepper to taste. Turn the pieces to coat evenly, then turn the chicken skin side up. Tuck the lemon slices and potatoes in between the chicken pieces.
Bake the chicken for 45 minutes. Baste with the pan juices. Continue to bake, basting occasionally, for 15 to 30 minutes longer or until the chicken is browned and the potatoes are tender.
Transfer the chicken, potatoes, and lemon slices to a serving platter. Tip the pan and skim off the fat. Pour the juices over the chicken and serve.