Heat oil in a large sauté pan or Dutch oven over high heat. Once oil is hot, add ribs and sear until browned on each side. Remove and set aside.
Lower heat to medium. Add leeks and prunes to the pan. Sauté until leeks are golden at the edges and prunes are fragrant, about 7 minutes. Add red wine, red wine vinegar and let simmer for two minutes to reduce slightly. Add olives, capers, garlic, brown sugar, and oregano.
At this point, you can either add the ribs back to the pan (if it is large enough), cover, and transfer to the oven. Or you can add the ribs to a separate baking pan and pour the sauce over it.
Bake for about 3 hours (times will be different depending on the pan used, watch your meat), until ribs are tender and the meat is pulling away from the bone. This freezes and rewarms well.