Add the Oreo cookies, milk, and ice cubes to your blender.
Secure the lid and blend on high speed until the mixture is smooth and creamy with some small cookie bits visible.
Stop the blender and check the consistency—if it’s too thick, add a splash more milk; if it's too thin, add a few more ice cubes or cookies and blend again briefly.
Pour the slushie into glasses, watching the dark, chocolatey color and thick, icy texture settle in.
Optionally, top with whipped cream or extra crushed Oreos for decoration.
Serve immediately with a straw or spoon, enjoying the cold, crunchy contrast and rich Oreo flavor.