Preheat the oven to 350F degrees and spray a 9"x 13" baking pan with non-stick spray or line it with parchment and set it aside.
Mix the brownie mix, eggs, vegetable oil and water together in a bowl and set aside.
Press the cookie dough into the pan in an even layer. Next, add a layer of the Oreo cookies (you'll need to cut some down to fit)
Finally, pour on the brownie batter and spread it evenly.
Bake for 35-45 minutes or until a toothpick comes out clean when inserted into the center of the brownies.
Remove the pan from the oven and let it cool for 10 minutes before slicing and serving.