Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a medium bowl, combine the rolled oats, flour, baking soda, salt, and cinnamon. Mix well and set aside.
In a large bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Beat in the egg and vanilla extract until well combined.
Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Fold in the chocolate chips until evenly distributed.
Drop rounded tablespoons of dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake for 10-12 minutes, or until the edges are lightly golden. The centers may look slightly underbaked; they will firm up as they cool.
Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.