Preheat the oven to 350°F (175°C).
Whisk together the flour, baking powder, baking soda, and salt in a medium bowl.
In a large bowl, whisk together the sugar, cocoa powder, and vegetable oil.
Beat in the eggs one at a time, followed by the vanilla extract.
Gradually mix in the dry ingredients until just combined, being careful not to overmix.
Cover the dough and refrigerate for at least 2 hours or overnight.
Roll the dough into balls, about 2 tablespoons each.
Coat each ball in confectioners’ sugar, then roll again to ensure a thick coating.
Place the balls onto a baking sheet lined with parchment paper, leaving about 2 inches of space between each cookie.
Bake for 9-14 minutes or until the edges are set and the centers are slightly soft.
Remove from the oven and let cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.