The following is the e-mail response from In-N-Out Burger when asked which of their menu items are vegan:
In response to your inquiry, we offer a Veggie and if ordered without spread, is considered vegan. The Veggie will come with lettuce, tomato, and onion just like our Hamburger, but does not contain a meat patty or meat substitute. You can also order it with ketchup and mustard instead of the spread.
Our french fries are also vegan, they are cooked in 100% cottonseed oil and are not shared with any other cooking spaces.
In response to your question, our buns contain no animal bi-products. If you need any further assistance, please call out toll-free Customer Service number: (800)786-1000.
Thanks again for taking the time to contact us.