Q: Is oatmeal gluten-free, or does it contain gluten?
A: Pure oatmeal does not contain gluten. However, most oatmeal brands on the market today are not pure — they contain oats that have been cross-contaminated with a tiny bit of wheat, barley and/or rye. Since those grains do have gluten in them, that cross-contamination makes most oatmeal brands unsafe on the gluten-free diet.
More information at this link: http://celiacdisease.about.com/od/glutenfreegrains/f/Is-Oatmeal-Gluten-Free.htm