Preheat oven to 350°F. Line a 9×9 baking pan with parchment paper or lightly grease.
Prepare the brownie batter according to the package directions. Pour the batter into the prepared pan and spread into an even layer.
Bake the brownie layer for 8 minutes.
While the brownies are par-baking, prepare the cookie dough. In a large bowl, cream together the butter, brown sugar, and granulated sugar until smooth and fluffy.
Add the egg and vanilla extract and mix until combined.
Stir in the flour, baking soda, and salt until just combined. Fold in the chocolate chips.
Remove the partially baked brownies from the oven and arrange 16 Oreo cookies in an even layer over the brownies.
Drop spoonfuls of cookie dough evenly over the Oreo layer. Gently flatten slightly, but allow some Oreo tops to remain visible.
Sprinkle the crushed Oreos evenly over the cookie dough.
Return the pan to the oven and bake for about 25 minutes, or until the cookie layer is lightly golden and the center is set.
Allow the brookies to cool completely before slicing into bars.