Place the potatoes, cut into 4 (or 2 if smaller), in a large tray. Add 2/3 cup olive oil, 2-3 garlic cloves, oregano, salt, black pepper, 2/3 cup water and squeeze out the juice of 1 lemon and 1/2 an orange.
Stir everything well.
Place the chicken at the very top, cut nearly into 2 but not all the way through. Bake at 374°F (190 °C) for about 40 min.
10-20 min. before you take it out of the oven, pour on the rest of the lemon and orange juices.