In a medium mixing bowl, mix together with a wooden spoon the brownie mix, vegetable oil, water and eggs until combined and no large clumps of dry brownie mix remain.
Spray the insert of either a 3.5 quart casserole slow cooker OR a 6 quart or larger slow cooker with non-stick cooking spray.
Cut open the roll of chocolate chip cookie dough and crumble the dough into little bits with your hands and place crumbles in the prepared slow cooker.
Pour the prepared brownie batter over the cookie dough bits and spread evenly.
Place a layer of paper towels or a clean flour sack kitchen towel between the lid of the slow cooker and the insert to prevent condensation from the dripping on the brownies while they cook.
Cook on HIGH for 45 minutes to 1 hour, or until the middle is still soft but not liquid.
Turn off slow cooker and allow the brownies to cool for at least 15 minutes before serving.