Peel a 1-inch strip around center of each potato. Place potatoes in a large bowl. Add butter and next 3 ingredients, tossing gently. Place potatoes on a lightly greased rack in a broiler pan.
Bake at 425° for 20 minutes; remove from oven.
Stir together breadcrumbs and next 5 ingredients. Moisten tenderloins with water; press crumb mixture over tenderloins, and place on rack with potatoes.
Bake at 425° for 25 more minutes or until potatoes are tender and a meat thermometer inserted into thickest portion of tenderloins registers 160°. Sprinkle potatoes with parsley, and slice tenderloins. Garnish, if desired.