Calling oats gluten-free is a bit controversial. Oats are not considered gluten-free in many countries. While oats on their own are gluten-free, they are often contaminated with other gluten-containing grains. In addition, some people with celiac disease are not able to tolerate oats, even if they have not been contaminated with gluten. In the US, oats are generally considered gluten-free and are typically labeled as such. In Canada, oats must be grown and processed in a certain way to prevent cross-contamination to be labeled gluten-free. They may also be called "pure oats". If you plan on serving oats to a person that follows a gluten-free diet, make sure to ask them whether they are able to consume oats first.