Preheat oven to 350 Line 9x13 baking dish with aluminum foil or parchment paper. Grease and flour. I use the spray.
Cookie dough: Cream the butter and both sugars in a large bowl. Add eggs and vanilla mix well. In a separate bowl, whisk together the flour, baking soda and salt then slowly incorporate into the mixer until just combined. Stir in chocolate chips. Spread the cookie dough in the bottom of prepared pan.
Top with oreo cookies. Mix brownie mix following directions on back of box and pour on top of the oreo cookies. Bake at 350 for 55 minutes, test. Mine took longer. Cool completely before cutting.