Combine 2 tablespoons chili powder, cilantro, oregano, cumin and garlic powder in small bowl. Coat lamb chops with spice mixture. Place lamb chops in glass baking dish. Cover and refrigerate 8 hours or overnight.
Heat 1 tablespoon oil in medium saucepan over medium-high heat. Add shallots and garlic and sauté 2 minutes. Add red wine, beef stock and remaining 2 tablespoons chili powder. Boil until sauce is reduced to 3/4 cup, about 30 minutes. Remove sauce from heat. Add butter 1 piece at a time, whisking until melted after each addition.
Prepare barbecue (medium-high heat) or preheat broiler. Grill or broil lamb chops to desired doneness, about 6 minutes per side for medium-rare.
Place 2 lamb chops on each of 4 plates. Spoon sauce over lamb and serve.