Crush the Oreos and mix with melted butter. Press into a 9x13-inch dish to form the crust.
In a bowl, beat the cream cheese, sugar, and 2 tablespoons milk until smooth. Fold in half of the Cool Whip. Spread over the crust.
In another bowl, whisk together the chocolate pudding mixes and 3 1/4 cups milk. Let it thicken, then spread over the cream cheese layer.
Top with the remaining Cool Whip. Chill for at least 4 hours, then slice and serve!