Place the Oreos in a food processor, and process in long bursts until they are in fine crumbs.
Combine the cookie crumbs with melted butter. Mix until it is the texture of wet sand.
Press the crust in an even layer into the bottom and up the sides of a pie or tart pan. If you want a crispier crust, bake it at at 350 F for 12-15 minutes.