Add the butter and sugar to a large mixing bowl. Using an electric mixer, cream the butter and sugar for about 3 minutes, until fluffy and lighter in color. Add the peanut butter and mix until combined. Add the egg and vanilla and mix until combined.
In a separate bowl, sift the flour, salt, baking powder and baking soda and stir to combine. Stir in the oats. Gradually add the flour/oat mixture to the sugar mixture, using a wooden spoon to stir just until combined. Do not over-stir.
Scoop the batter by the tablespoon to form 1-inch balls and place them on a cookie sheet. Press down on each one with a fork to create a criss-cross pattern.
Bake for 10 minutes. Remove from the oven and allow the cookies to sit for 2 minutes on the baking sheet before transferring them to a wire rack to cool.
Recipe by The Daring Gourmet at https://www.daringgourmet.com/whole-wheat-peanut-butter-oatmeal-cookies/