Old-fashioned rolled oats are best for making granola. Steel-cut and quick oats don’t have the right texture to complement granola. If making gluten-free granola, be sure that the rolled oats are specifically marked gluten-free. While oats are naturally so, they can become contaminated with gluten in the processing. Gluten-free oats cost a bit more, but are an important part of this recipe if making gluten-free for allergies, etc.