Preheat your oven to 350°F (175°C). This ensures your cookies bake evenly.
Line a baking sheet with parchment paper. This will help the cookies come off easily after baking.
In a medium bowl, whisk together the old-fashioned rolled oats, all-purpose flour, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, use an electric mixer to cream the softened butter and dark brown sugar together until the mixture is light and fluffy.
Beat in the egg and vanilla extract until well combined.
Gradually add the dry mixture to the wet ingredients, mixing just until incorporated. Be careful not to overmix.
Gently fold in the chopped pecans and raisins or currants until evenly distributed throughout the dough.
Using a cookie scoop or tablespoon, drop rounded balls of dough onto the prepared baking sheet, spacing them about 2 inches apart. Bake in the preheated oven for 10-12 minutes, or until the edges are golden and the centers look set but still soft.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Enjoy your delicious homemade oatmeal cookies!
