This was a big problem once I was diagnosed with Celiac Disease. I used to live on PB&J for a breakfast snack on the go at work. Lunch usually consisted of a sandwich (tuna, turkey, chickenbreast).
So now what?
I can't have bread, no pasta, can't go the cafeteria and risk cross contamination (that is, even if they had something that was GF). On top of that no kitchen, so it has to keep in the fridge or be easily heated in the nuke machine.
So this is what I have come up with so far, hopefully it helps you.
1. SALAD, no shit. But I have come up with variations with tuna, chicken, salmon, nuts, cheese. Use your imagination but it is possible to make a salad at work more than a boring pile of lettuce.
2. Quinoa. I have done it cold and heated. The leftover dinner is usually an easy lunch. Usually sauted onions &/or peppers mixed in. My new cold dish is a take on the greek salad. Quinoa with olives, cucumbers, tomatoes, feta cheese and a little drizzle of a vinaigrette (I make my own but you could use any salad dressing out there).
3. Left over pizza. I'll get to my pizza story sometime but Sunday night is usually pizza night. I make extra and bring in a few slices for lunch.
4. Antipasti. I have made a few platters of salami, cheese, roasted peppers. It's nice to have some variety and pick and choose from the pieces on the platter. I'll load up at the deli on the weekend and make a platter for an easy lunch one night when I'm tired. No cooking required. I like Molinari meats. I contacted the company and they said all of their meats are GF.
5. Chicken. How many ways can you skin a bird? My kid likes chicken nuggets so my wife gets chicken tender strips and breads them in a GF breading. He eats them and I get to bring them to lunch. Eat them hot, cold, plain, with BBQ sauce. I'll sometimes make a side of Kasha, you might know it as Buckwheat, but contrary to the name there is no wheat in it, its actually a fruit. It's a nice grain, nutty in flavor and about the size of barley but not as mushy.
Well, that gets you a few days. Hope it helps. I'll post more as I come up with new ideas.