This restaurant just opened less than two weeks ago. It's a national chain with most locations concentrated in the Eastern part of the U.S. They have an insert in their regular menu for Gluten Free Pizza. When I asked about other things on the menu being gluten free (like their many salads), the manager told me they technically ARE (including all dressings) with the exception of things like croutons, BUT they are not prepared in a separate area the way the pizza is. So they don't "guarantee" them being gluten free (but they will change their gloves and take every precaution). They do guarantee that the pizza is GF.
The pizza was good -- not the best gluten free pizza we've ever had, but not bad either. And there are a lot of combinations to choose from, or you can "create your own." It's a fairly thin crust and a nice size, too -- 12 inches, 8 pieces. The place was packed for lunch, and it's just nice to have a popular new place like this to go with friends and where we can order safe, GF pizza.
BTW, not sure how the "Mellow Mushroom" name originated, but the mushroom soup unfortunately is NOT gluten free!