Preheat oven to 400F. Cook pasta according to package directions. Place squash in a saucepan: add water to cover. Bring to a boil. Cook covered until tender, 8-10 minutes.
Meanwhile, place yogurt, milk, salt, pepper and nutmeg in a blender. Drain squash & transfer to blender; cover & process until pureed. Return mixture to saucepan and heat through, stir in cheeses until melted.
Drain pasta; add to squash mixture. Toss to coat. Transfer to greased 8-in. square baking dish. Sprinkle mixture with bread crumbs.
Bake, uncovered until golden brown, 15-20 minutes.
