Bring squash and water to cover to a boil; cook 30 minutes or until tender.
Remove from heat; drain. Mash until smooth.
Melt 1 tablespoon butter in skillet.
Add onion and garlic; saute 5 minutes or until tender.
Remove from heat; stir in squash, 2 tablespoons butter, eggs, and next 3 ingredients. Fold in cranberries. Spoon into lightly greased 1-quart baking dish.
Combine breadcrumbs and remaining 1 tablespoon butter.
Sprinkle over casserole.
Bake at 375 for 1 hour and 15 minutes or until set and golden.