Place 1 in. of water in a large saucepan; add carrots. Bring to a boil. Reduce heat; cover and simmer for 7-9 minutes or until crisp-tender. Drain, reserving 1/4 cup cooking liquid. Transfer carrots to a 1-1/2-qt. baking dish.
In a small bowl, combine the mayonnaise, onion, horseradish and reserved cooking liquid; spread evenly over carrots. Sprinkle with cheese; top with bread crumbs. Bake, uncovered, at 350° for 30 minutes. Yield: 8 servings.