Leave the cookies intact – do not remove the filling. Finely crush the Oreo cookies using a food processor, using the blade attachment.
Add the melted butter, and continue to process until the crumbs are fine and start to stick together.
Alternately, place the cookies in the bottom of a large zip top plastic bag – the freezer kind are stronger – and seal the bag, leaving a small space open for air to escape. Using a rolling pin, or the flat side of a meat mallet, beat the cookies until they are finely crushed and start sticking together. Pour the cookie crumbs into a large mixing bowl and blend in the melted butter.
Press the cookie mixture into the bottom and up the sides of a pie plate. (I use the flat bottom of a metal measuring cup to smooth out and push the crumbs into place in the pie plate, but you can use your fingers if you like.)
Chill the crust for 30 minutes to an hour until ready to fill. (Alternately, for a crisper crust, bake the crust for 8-10 minutes at 350°F, then allow to cool completely before filling.)