Talk with your server and they will bring you the Gluten Free menu which is also available at http://www.brinker.com/gr/allergens/otb%20allergen.pdf
Concerns about cross-contamination are addressed in the list of suggested beverage and menu options:
We have prepared this suggested list of beverage and menu options based on the most current ingredient information from our food suppliers and their stated absence of wheat/gluten within these items. Please be aware that during normal kitchen operations involving shared cooking and preparation areas, including common fryer oil, the possibility exists for food items to come in contact with other food products. Due to these circumstances, we are unable to guarantee that any menu entrée can be completely free of allergens, including tortilla chips and enchiladas.*Over the past few years, we have noticed that the servers are more and more familiar with Gluten Free. It used to be a struggle to explain what we needed for our daughter and ordering usually took a significant amount of time. However, it is much easier now.
Special thanks to Jason Helms from the kitchen at the Cary location for always taking the time to talk with us about our daughter's needs when eating out. He never made my daughter feel uncomfortable about being different; he has always made our daughter feel special and important! He is one of the reasons that we keep going back to On the Border.
Typically, we create a meal from side items and the kids menu for our daughter. However, the salads and fajitas are flavorable and filing for adults and older children.
As a related note, you can also get allergen information about egg, fish, dairy, peanut, shellfish, soy, and tree nut from the website.