Can fresh winter squash be frozen?

Yes. Although winter squash keeps for long periods of time in cool, dry spaces, to save it long-term, some consumers may prefer to freeze it. Before freezing, the squash should first be cooked. Options include boiling and baking. After cooking the squash, you also may wish to purée it.
 
Before cooking, cut the squash into quarters and scoop out the seeds and stringy pulp. After the squash is cooked, store it in a freezer-ready plastic container or sealable plastic bag. Squeeze out excess air from the bag to avoid freezer burn. Fill the container close to the top, but leave a little head room for expansion. Cooked, frozen winter squash will keep for up to a year.
 
Source(s):
Whole Foods "Guide to Vegetables"
Ehow.com "Best Way to Store Squash"