Note: Marinate these beef and pork tenderloins together, but cook them separately.
Sandwiches can be prepared from either or both types of meat. Place tenderloins in a large pan or dish; Pour marinade over top, and cover tightly. Refrigerate overnight, turning meat several times; drain. Place beef tenderloin, fat side up, on rack in a shallow roasting pan; rub with 1 tablespoon vegetable oil. Bake at 450 degrees for 15 minutes. turn oven off; do not open door. Let roast remain in oven 45 minutes. (roast will be medium rare). Place pork tenderloins, fat side up, on rack in a shallow roasting pan; rub with 1 teaspoon vegetable oil. Bake at 325 degrees for 1 hour or until well done. Slice tenderloins, and place on serving platter. Serve on party rye bread with endive; top with mayonnaise, barbecue sauce, Marinade: Combine all ingredients in a small mixing bowl, mixing well.