Mix the two boxes of instant pudding with 4 cups milk, whisking well. Put to the side until pudding thickens.
Crush the Oreo cookies in your food processor, or if you don't have, place in a Ziplock bag and crush with a rolling pin.
Add the melted butter to the cookie mixture and mix well until combined.
Press the cookie mixture into the bottom of a 9x13 pan, covering the entire bottom.
Blend cream cheese, butter and powdered sugar until smooth. Fold in one (1) of the Cool Whip containers.
Pour this over your cookie crust for second layer.
Next add the thickened pudding for third layer.
Top the dessert with the other Cool Whip container for fourth layer.
Refrigerate for at least one hour. Garnish with lemons.