Preheat your oven to 350°F (175°C). Line a 9x13-inch pan with parchment paper.
In a large bowl, whisk together melted butter, brown sugar, and granulated sugar until smooth.
Add eggs and vanilla extract. Mix until well combined.
Stir in flour, baking soda, and salt until a soft dough forms.
Fold in chocolate chips.
Press the cookie dough evenly into the bottom of the prepared pan.
Top with an even layer of Oreo cookies.
Prepare brownie batter according to package instructions. Pour over the Oreos and spread evenly.
Bake for 35-40 minutes, or until the top is set and a toothpick inserted into the brownie layer comes out mostly clean.
Cool completely before slicing for clean edges.