Beat butter, brown sugar, and white sugar together in a bowl using an electric mixer until smooth and creamy. Beat eggs and vanilla extract into butter mixture until incorporated.
Whisk oats, flour, chocolate chips, cocoa powder, baking soda, and salt together in a bowl; slowly stir into butter mixture until dough is just mixed. Scoop dough using a small scooper onto baking sheet.
Bake in the preheated oven until edges of cookies are lightly browned, about 15 minutes.