To make these Raisin Pecan Oatmeal Cookies gluten-free, replace the all-purpose flour with a certified gluten-free 1:1 baking flour blend. Use certified gluten-free old-fashioned oats, as regular oats are often processed on shared equipment with wheat. Confirm that the pecans, raisins, baking powder, vanilla extract, sugars, butter, eggs, cinnamon, and salt are labeled gluten-free and free from cross-contact warnings. Use clean mixing bowls, baking sheets, parchment paper, measuring tools, spatulas, and cooling racks to prevent gluten contamination.