Preheat oven to 350 degrees.
Stir together white sugar, cocoa powder and vegetable oil.
Beat in the eggs one at a time, then add vanilla.
Combine the flour, baking powder, and salt in a small bowl.
Stir flour mixture into the cocoa mixture.
Cover bowl and chill for 4 hours or more.
To avoid sticking, line cookie sheets with parchment paper or reusable baking mats.
Roll dough into one inch balls. (I like to use a number 50 size scoop.)
Roll each ball in powdered sugar and place on the baking sheet.
Bake 10 to 12 minutes.
Let cool on baking sheet for 2 minutes before transferring to wire racks to fully cool.