Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a large bowl, cream the softened butter and granulated sugar together until light and fluffy, about 3-4 minutes.
Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Gently fold in the blueberries and oats (if using), being careful not to crush the berries.
Drop tablespoon-sized portions of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake for 12-15 minutes, or until the edges are lightly golden.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.