How to Make It
Preheat the oven to 300°. If you have an unglazed clay pot like a Römertopf, soak it in warm water for 30 minutes. Pat dry.
Meanwhile, heat the olive oil in a large skillet. Season the lamb with salt and pepper. Add half of the lamb to the skillet and cook over high heat until browned, about 10 minutes. Transfer the lamb to the clay pot or a medium enameled cast-iron casserole. Repeat with the remaining lamb.
Pour off the fat in the skillet. Add the water and bring to a boil, scraping up any browned bits stuck to the bottom. Pour the liquid into the clay pot and add the peppers, tomatoes, onions and oregano. Cover and bake for 2 hours and 15 minutes, or until the lamb is very tender.
Pour the stew into a large strainer set over a large saucepan. Skim the fat from the juices. Boil the juices until reduced to 3/4 cup, about 10 minutes. Return the lamb and vegetables to the sauce and cook just until warmed through.