Preheat your oven to 350°F (175°C).
In a large bowl, whisk together the all-purpose flour, rolled oats, brown sugar, granulated sugar, baking soda, ground cinnamon, and salt until well combined.
In a separate bowl, cream the softened unsalted butter until smooth and fluffy.
Add the egg and vanilla extract to the creamed butter and beat until fully incorporated.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined to form the cookie dough.
Drop rounded tablespoons of dough onto an ungreased baking sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 10 to 12 minutes, or until the edges are golden brown but the centers are still soft.
Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.