Happy Thanksgiving Cathy,

Your mushroom caps won't freeze well, but you should be able to freeze the stuffing. To speed up assembly later you can freeze portions of stuffing sized for the mushroom caps individually on cookie sheets then bag them after they become solid. (I'm assuming your stuffing will have all cooked ingredients in it.) Thaw the stuffing mounds before baking or you'll have to cook the mushrooms too long to get the stuffing to temperature.

As an experiment for future reference, freeze one cooked and one raw stuffed mushroom using your recipe and see how you like the results. Undercook the cooked mushroom to allow for extra cooking while heating it later. Again, I would thaw both before cooking/heating.

Here are some tips from the Mushroom Information Center:

Storing Mushrooms:
Always keep mushrooms refrigerated. They're best when used within several days after purchase but will keep up to a week. Do not rinse mushrooms until ready to use. If purchased loose, store mushrooms in a paper bag. If purchased in packages, do not open until ready to use; store unused portion in a paper bag. Storing in air-tight containers or plastic bags will cause condensation and speed spoilage.

Happy Holiday Cooking!

Betsy