Preheat oven to 350°F (175°C). Line a 9x13-inch pan with parchment paper.
Prepare brownie batter as directed on the box and spread evenly into the prepared pan.
In a large bowl, beat softened cream cheese and sugar until smooth.
Add eggs and vanilla extract, and mix until combined.
Fold in the roughly chopped Oreos, then spread the cheesecake mixture evenly over the brownie batter.
Sprinkle crushed Oreos on top.
Bake for 35–40 minutes, or until the center is set and edges are slightly golden.
Cool completely before slicing into bars. Chill for cleaner cuts if needed.