In a large bowl, combine the egg, oats and soup mix. Crumble beef over mixture and mix well. Shape into 1-in. balls.
Place 1 in. apart on a greased rack in a shallow baking pan. Bake at 400° for 18-20 minutes or until no longer pink. Drain on paper towels.
In a large skillet, combine the apricot nectar, brown sugar, ketchup, vinegar, mustard and horseradish. Bring to a boil. Reduce heat; simmer, uncovered, for 10 minutes. Add meatballs; simmer 15 minutes longer or until heated through. Sprinkle with parsley.