How to freeze summer squash:
Sliced: Choose young squash with tender skin. Wash, slice or cube; blanch three minutes. Cool immediately in cold water, drain and put into freezer containers. Freeze.
Mashed: Wash, slice and cook in a very small amount of water until just tender. Mash. Pour into a bowl, set in ice water to cool quickly. Package and freeze. Frozen summer squash works best in baked goods recipes.