Crush the Oreo cookies in a food processor or in a zip-top bag with a rolling pin until fine crumbs form. Mix with melted butter until evenly coated. Press firmly into the bottom of a 9x13-inch baking dish or pie dish to form the crust. Chill in the refrigerator while preparing the filling.
In a medium bowl, beat the softened cream cheese and powdered sugar until smooth and creamy. Fold in the whipped topping until fully combined. Spread this layer evenly over the chilled Oreo crust.
In another bowl, whisk together the chocolate pudding mix and cold milk for 2 minutes, or until thickened. Let sit for 5 minutes, then pour and spread over the cream cheese layer.
Spread the remaining whipped topping over the pudding layer. Smooth the top with a spatula. Garnish with crushed Oreos or mini Oreo cookies.
Refrigerate the pie for at least 4 hours or overnight to allow the layers to set. Slice and serve chilled for best results.