In-and-Out Burgers is probably is probably the best fast food chain in California, Nevada, And Arizona. When I lived in California, I was near the northermost In-and-Out and ate there regularly. The parking lot seemed to be filled with out-of-state license plates, particularly people from who wanted one last In-and-Out burger before they returned home.

Burgers can be ordered "protein style", wrapped in a lettuce leaf rather than served in a bun. French fries is the only fried food served and buns are not baked on the premises, thus avoiding those causes of cross contamination. The company web site does not provide any information about food sensitivities or allergies, but my own personal experience suggests that everything is celiac friendly. I know the burgers are great!