I recently ate a very simple meal of Bell & Evans chicken and vegetables and developed a migraine immediately afterward. This is one of my possible reactions to gluten, and it was also the first time I had ever eaten this brand of chicken.
If you haven't already checked that link mentioned above you might want to. Read the part about the link between hydrolyzed proteins and MSG. I know I am sensitive to MSG, and it says that when they hydrolyze the meat and dairy proteins they break apart and form MSG. It won't be listed as MSG on the package, because MSG was not added to the meat, it was created in the processing. So maybe that is the reaction you are having and it is not from gluten after all. Just a thought.