Preheat the oven to 350 degrees. Add the cake mix, flour, sugar, melted butter, sour cream, and milk to a mixing bowl. Mix on medium speed for two minutes.
Add cake to a 9x13 greased pan. Bake the cake for the time according to the back of the package.
Remove from the oven and cool on a rack until the cake is warm to the touch.
Using a wooden spoon, poke holes evenly throughout the cake.
Next, mix the Oreo Pudding according to the package directions. Allow to sit for 5 minutes and then pour over the top of your poked holes in the cake.
Chill the cake for 30 minutes to 1 hour before adding whipped topping
Remove the cake from the fridge and spread thawed whipped topping over the cake to the edges.
If you’re ready to serve, add Oreos now OR chill until ready to serve – adding the Oreos right before you’re ready to eat. Once ready to eat, break up the Oreos and add right over the cake. Serve immediately.