To make this recipe gluten free, use certified gluten-free hoagie rolls or sandwich rolls. Also verify that the French onion soup, beef broth, Worcestershire sauce, and beer are labeled gluten free, since these ingredients often contain gluten or may be subject to cross-contact. If preferred, replace the beer with additional gluten-free beef broth. When preparing the sandwiches in a shared kitchen, use clean utensils, cookware, and surfaces to avoid gluten contamination.