Crush 10 Oreos to crumbs using the food processor. Add them to the ice cream. Then add 10 more Oreos to the food processor and pulse them just a few times so that they are crushed but still in large pieces. Add these to the ice cream as well.
Pour the ice cream into the prepared pie plate, laying whole Oreos on the top of the pie before covering tightly with plastic wrap. Freeze for at least 4 hours.