Preheat oven to 350F degrees. Spray a 9x13-inch baking pan with nonstick cooking spray.
Prepare 1 box chocolate cake mix with ingredients needed to make cake (eggs, oil and water) according to package directions and bake cake according to times on the back of the box.
When cake is finished, allow to cool for about 10 minutes, then poke holes all over cake (about 1-inch intervals) using a wooden spoon handle.
In a medium bowl, add 3 cups milk to 2 (4 ounce) packages Instant Oreo pudding and whisk until most of the lumps are removed. There will be a few lumps in the pudding because of the Oreo pieces that are in the pudding.
Pour pudding mixture over cake making sure to aim for the holes.
Spread it out with a spoon and gently push down on the pudding to help get it into the holes.
Then put the cake in the refrigerator to allow it to cool completely. About an hour.
Spread 8 ounce tub whipped topping, thawed on top of pudding layer.
Once it is set, top with crushed Oreo cookies. Slice then serve.