Preheat your oven to 350°F (175°C).
Cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.
Add the large egg and vanilla extract, then beat until well combined.
In a separate bowl, whisk together the all-purpose flour, rolled oats, baking powder, baking soda, salt, and ground cinnamon.
Gradually add the dry mixture to the wet ingredients, stirring gently until just combined.
Fold in the fresh blueberries gently.
Scoop rounded balls of dough onto a parchment-lined cookie sheet, spacing them apart.
Bake for 10-12 minutes until edges are lightly golden and centers look set.
Let cool on the baking sheet for about 5 minutes before transferring to a cooling rack.
