Preheat oven to 350°F.
Crush Oreos and mix with 4 tablespoons melted butter. Press into the bottom of a 9x13 inch baking pan.
Bake for 7 minutes.
While the Oreo crust is baking, mix the softened mint chocolate chip ice cream and Cool Whip together until well combined.
Spread the ice cream mixture over the warm Oreo crust.
Cover with foil and freeze for at least 8 hours or overnight.
Cut into slices and serve.
