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Here's another Bob to chime in on Fran's question! I too have found
that people will be as accommodating as they know how to be. My
co-workers have been very supportive; one of them asked me for a good
recipe for me to eat for my birthday and bought what she needed and
fixed a delicious gf chocolate-mocha torte (recipe courtesy of this
list) which we all enjoyed. The committee for another party asked me
to bring finger food that I could eat (I brought corn chips, rice
crackers, and gf dips and salsa--someone else was bringing fresh
fruit) and submit the expense as part of the party budget; the set-up
committee made sure to put my gf offerings at one end of the table,
away from the other crackers and stuff, and even labeled it wheat-
and gluten-free! (I suspect that someone brought over a Trisket or
something and dipped it in one of my dips, though, as I got fairly
sick later.)

For the winter holidays, we are having a catered buffet at the
holiday party. As luck would have it, my supervisor was tapped to
arrange the menu with the caterer, so she asked me go along with her
and another committee-member to discuss the menu! Although the food
includes lots of fried (and breaded) stuff, there are several nice
dishes I can have, and the caterer was happy to answer all my
questions about ingredients,  food preparation, and handling. Being
in on the planning stages may involve sacrificing more of your time
than you always feel you have, but the peace of mind and the power to
give your own input more than make up for it.

So, bring your own stuff if you need to, join the planning committees
if you can, contact the food provider ahead of time if you can, and
have a good time!

Happy Holidays, Good Luck and Good Health!
Bobbi in Baltimore