Required company holiday party with open bar. Can a recoving alcoholic legally avoid attending?

My short answer is that yes you can use your medical/disability condition (alcoholic) as a reason to avoid the holiday party where there will be drinking.  This would be deemed a reasonable accommodation.  The question is whether your boss or HR department is aware of your condition.  As the party is a requirement, you will need to inform someone, be it HR, or whoever would be designated at the company to review a medical or disability request for an accommodation. If you have questions or run into a problem with the employer over this, you should immediately speak to an attorney.