To make this recipe gluten free, replace the all-purpose flour with a high-quality 1:1 gluten-free baking flour blend that contains xanthan gum or a similar binder. Also verify that the baking powder and chocolate chips are certified gluten free, as ingredients and manufacturing practices may vary by brand. Because gluten-free flour blends can affect texture, check the bars a few minutes early and avoid overbaking to help maintain a soft, chewy result.