HEAT oven to 325°F.
BEAT whipping cream with mixer on high speed until soft peaks form. Mix steak sauce, onions and horseradish in medium bowl. Add whipped cream; stir gently until well blended. Cover. Refrigerate until ready to use.
PLACE meat in roasting pan.
BAKE 45 min. to 1 hour 15 min. or until done (160°F). Cut meat into thin slices. Serve with horseradish sauce.