Heat the oven to 375ºF.  Cut the tops off the peppers and reserve.  Remove and discard the core and seeds.  Place the peppers, cut-side up, into a 3-quart shallow baking dish.Heat the oil in a 10-inch skillet over medium-high heat.  Add the turkey and cook until browned, stirring often to separate meat.  Add the onion and garlic and cook until tender.  Stir in the sauce, cheese and black pepper.  Spoon the turkey mixture into the peppers.  Top with the reserved pepper tops, if desired.Bake for 40 minutes or until the peppers are tender.