Step 1: Preheat your oven to 350°F (175°C).
Step 2: In a mixing bowl, whisk together the all-purpose flour, baking soda, and salt.
Step 3: Cream together the softened unsalted butter and peanut butter using an electric mixer. Gradually add in the granulated sugar and brown sugar until light and fluffy.
Step 4: Add in the egg and vanilla extract. Mix until fully incorporated.
Step 5: Gradually add the dry mixture to the wet mixture, mixing until just combined.
Step 6: Gently fold in the rolled oats and Reeses Pieces until evenly distributed.
Step 7: Drop rounded tablespoons of dough onto a baking sheet lined with parchment paper, spacing them about 2 inches apart. Bake for 10-12 minutes or until edges are lightly golden.
Step 8: Allow cookies to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.
