Preheat the oven at 350o F.
We peel the potatoes, rinse, and drain and cut them into chunks.
Then we rinse the meat, drain and put it in a deep baking pan. Add to the pan the potatoes, oregano, salt and pepper to taste and mix. We pour over the olive oil, lemon juice and water. Cover the pan with aluminum foil.
We bake in the preheated oven for about 1 hour, until both meat and potatoes are tender. Then remove the aluminum foil and continue baking for an additional 15-20 more minutes, until browned. We may add some more boiling water if needed.
Remove the pan from the oven and serve the “arnaki psito me patates”, garnished with rosemary.
If you have time, you could marinate the lamb: Put in a bowl 2 cups of olive oil, 1/2 cup of wine and 2 rosemary sprigs. Add the lamb and cover the bowl. Leave it in the fridge for about 1-2 hours