Make a lengthwise slit about three-fourths of the way through tenderloin; open tenderloin so it lies flat. Flatten to 1/4-in. thickness; set aside. , In a small skillet, saute onion in butter until tender. Add bread crumbs; saute until crumbs are golden brown. Remove from the heat. Stir in the parsley, sage, rosemary, salt, pepper and enough egg to moisten the ingredients. , Spread stuffing on one long side of tenderloin to within 1/4 in. of edges. Close meat and place bacon on top; tie with kitchen string. Place on a rack in a shallow roasting pan. , Bake, uncovered, at 350° for 50-60 minutes or until a thermometer reads 160°. Let stand for 5 minutes before slicing.