Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, combine the rolled oats, flour, granulated sugar, brown sugar, cocoa powder, baking soda, and salt until well blended.
In a separate bowl, mix the melted butter, egg, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Gently fold in the chocolate chips until evenly distributed throughout the dough.
Scoop tablespoons of dough onto the prepared baking sheet, leaving space between each cookie for spreading.
Bake in the preheated oven for 10 minutes, or until the edges are set and the tops look slightly cracked.
Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.