Preheat your oven to 350°F (175°C).
In a mixing bowl, combine the peanut butter, sugar, egg, vanilla extract, and baking soda until smooth.
Fold in the Reese’s Pieces.
Drop spoonfuls of dough onto a baking sheet lined with parchment paper.
Bake for 10-12 minutes or until the edges are lightly golden.
Allow to cool on the baking sheet for a few minutes before transferring to a wire rack.