Preheat oven to 350°F. Remove and reserve the filling from about 30 Oreo cookies. Crush the cookie wafers into fine crumbs and measure 2½ cups. Crumble 6 additional Oreo cookies and set aside for the cream cheese layer. Crumble the remaining 6 Oreo cookies and set aside for garnish.
Combine the Oreo cookie crumbs and melted butter in a medium bowl. Spread evenly into a 15 x 10-inch baking dish and gently press into an even layer. Bake for 12 minutes. Place on a cooling rack for 15 minutes, then transfer to the freezer for 18–22 minutes.
While the crust cools, combine the cream cheese, reserved Oreo filling, powdered sugar, and milk in a mixing bowl. Beat with an electric mixer or stand mixer until smooth and creamy. Fold in 4 ounces of the whipped topping, then fold in the 6 crumbled Oreo cookies.
Spoon dollops of the cream cheese mixture over the chilled crust. Using the back of a large spoon, gently spread into an even layer, taking care not to dislodge the crust.
Whisk the pudding mix and cold milk together until smooth. Pour over the cream cheese layer and spread evenly. Refrigerate for at least 15 minutes, or until the pudding begins to set.
Spread the remaining 8 ounces of whipped topping over the pudding layer.
Sprinkle the remaining crumbled Oreo cookies evenly over the whipped topping.
Refrigerate until fully chilled and ready to serve.