In a large mixing bowl, combine the brownie mix, flour, eggs, and vegetable oil. Stir until fully combined. The dough will be very thick.
Place the powdered sugar in a small bowl.
Scoop the dough into balls and roll each one in the powdered sugar until completely coated.
Place the cookies 2 inches apart on an ungreased baking sheet.
Bake for 8–10 minutes, until the cookies are set.
Let the cookies cool on the baking sheet for 5 minutes.
Transfer to a wire rack to cool completely.
Notes
*Store these cookies in an airtight container at room temperature for up to 1-2 weeks. Keep a piece of bread in the container with the cookies to keep them moist while you store them.