I've been a fan of Joe's since my first visit back around 2001 in Austin, TX. Obviously, if you have a seafood allergy, this is not the place for you, but Joe's has a great line of steampots and other tasty dishes. So, how does this establishment stack up for those of us avoiding wheat/gluten? Surprisingly well. As with most restaurants (especially chains) their food is all prepared in one common kitchen, and they do have a statement possible contamination from other food products. You can download a PDF version of their menus including their gluten free menu and nutritional information from their website under "Menu" (duh).
The good news? All of their Steampots and Buckets of Crab are gluten free. They mention the simply steamed and garlic herb versions in the individual descriptions, but list all the seasonings on the gluten free menu. I would ask a manager before choosing a different seasoning. I was able to find out from a forum on Celiac.com that Old Bay Seasoning is gluten free. I was also able to dig up a post on myglutenfreenj.com that actually has an email from Joe's Crab Shack stating what items were gluten free.
Obviously steer clear of their fried menu items as they're battered and therefore have wheat, but honestly, their gluten free options are also their healthier options anyway.
Keep in mind that they do serve and prepare a lot of items with butter, so if you're allergic to dairy be sure to talk to your server about your options.