1Spray 5-quart slow cooker with cooking spray. In slow cooker, place carrots and onion. Top with beef. Sprinkle with spices from packet. In medium bowl, mix both cranberry sauces and soup mix; spoon over beef.
2Cover; cook on High heat setting 1 hour. Reduce heat setting to Low; cook 8 hours longer or until beef is tender.
3In small bowl, mix sour cream and horseradish until blended. Cover; refrigerate until serving time.
4Remove beef from slow cooker to serving platter; cut across grain into thin slices. Spoon carrots and onion around beef. Drizzle with cooking liquid, if desired. Sprinkle with parsley and pepper. Serve with horseradish sauce.