Place meat in large glass dish; sprinkle evenly with pepper. Pour Italian dressing over meat; cover and marinate in refrigerator at least 1 hr.

Preheat oven to 325 degrees. Remove meat from marinade; discard marinade. Place meat, fat side up, in shallow roasting pan. bake 2 to 2 1/2 hr or until meat thermometer inserted into thickest part of meat registers 130 to 135 degrees for medium-rare doneness. Remove from oven. Cover and let stand 20 min before carving.

Meanwhile, mix 1 cup of the mayo and horseradish in small serving bowl. In another small serving bowl, mix remaining 1/2 cup mayo, honey mustard dressing and thyme. Serve sauces with meat. Makes 15 servings, 4 oz meat and 2 tablespoons sauce each.