Make Ahead: Store in an airtight container at room temperature for up to a week. In an airtight container in the refrigerator, they can last up to 2 weeks. Can I Use Old-Fashioned Oats? You can—it just depends on what texture you prefer for your no-bake cookies. Quick-cooking oats are smaller and absorb liquid more easily, which makes the cookies more soft and chewy. If you use old-fashioned oats, the cookies will have a less chewy texture.