Mix sugar, cocoa, and oil together in a medium bowl. Beat in eggs, one at a time, until combined. Stir in vanilla.
Combine flour, baking powder, and salt in another bowl. Gradually stir dry ingredients into the wet ingredients until thoroughly mixed. Cover dough and refrigerator for at least 4 hours.
Preheat the oven to 350 degrees F (175 degrees C). Line two baking sheets with parchment paper.
Roll or scoop chilled dough into 1-inch balls. Coat each ball in confectioners' sugar and place 1 inch apart on the prepared cookie sheets.
Bake in the preheated oven for 10 to 12 minutes. Let stand on the cookie sheet for a few minutes before transferring to wire racks to cool.
Repeat Steps 4 and 5 to make remaining batches.
