Put Oreos through the food processor to make crumbs. Reserve 1 cup cookie crumbs. Mix the melted butter with the remaining cookie crumbs and press into a 13x9 baking pan. Bake 15 minutes at 350 degrees. Cool completely.
Using a mixer, blend together cream cheese, sugar, peanut butter and 1/2 of the Cool Whip. Spread over cooled crust. Mix the pudding mix with the 3 cups milk and spread over cream cheese/peanut butter mixture. Cool completely. Then spread the remaining Cool Whip over the pudding layer. Sprinkle the reserved cookie crumbs on top. Chill until ready to serve. Cut into 16 pieces as it is very rich.