Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, combine the rolled oats, flour, baking soda, salt, and cocoa powder. Mix well and set aside.
In another bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Beat in the egg and vanilla extract until well incorporated.
Gradually add the dry mixture to the wet mixture, stirring until just combined.
Fold in the chocolate chips until they are evenly distributed throughout the dough.
Using a tablespoon or cookie scoop, drop spoonfuls of the dough onto the prepared baking sheet, spacing them about 2 inches apart.
Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centers are soft.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a cooling rack to cool completely.