In a large bowl, cream the butter and both sugars together for three to five minutes. Add the eggs and vanilla and mix to combine.
In a separate bowl, whisk the flour, baking soda and salt. Add the flour mixture to the butter and sugar mixture and mix on low until just combined. Stir in the chocolate chips.
Preheat oven to 350°F. Line a 9x13-inch baking dish with tin foil and coat it with non-stick cooking spray.
Place the cookie dough in the baking dish and flatten it into an even layer. Top the cookie dough with an even layer of Oreos.
Make the brownie batter following the instructions on the box. Add the fudge topping and stir to combine. Pour the batter over the Oreos and cookie dough in the pan.
Cover the baking dish with foil and bake the bars for 30 minutes. Remove the foil and bake for 15 to 25 minutes longer. Cool the bars completely before slicing and serving.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.