Preheat oven to 350°. Prepare cookie sheets with parchment paper or silicone baking mats.
In a large bowl, use an electric mixer to beat the butter and sugars together for 2-3 minutes. Add the vanilla and eggs and beat for another 2-3 minutes.
In a separate bowl, mix the flour, cocoa powder, baking powder, baking soda, and salt. Add the dry ingredients to the butter mixture and mix just until combined. Add the oats and stir just until combined.
Use a tablespoon-sized cookie scoop to drop the cookie dough onto the prepared cookie sheets (about 2 inches apart). Bake for 10-11 minutes. Let the cookies cool for a few minutes before transferring to wire racks to cool completely.