Their online menu clearly lists what items are gluten free or not. Ther gluten free buns are among the best I've never tried.
While they are good about labeling gluten free items, there have been times I found onion ring flour (not gluten free) in my fries so I would not order them if you are celiac or very sensitive with cross contamination. I have never had an issue with the burgers though!
— Somewhat
— Gluten-free items are marked on the main menu
— Some
— Excellent