Place the Oreos into a blender and pulse a few times to crush them into smaller pieces.
Add the cold milk to the crushed Oreos in the blender and blend on high until the cookies are fully broken down and the mixture is smooth.
Pour in the ice and blend again until the mixture is thick, frosty, and has a slushy consistency with tiny cookie bits visible throughout.
Stop the blender and give the slushie a quick stir to ensure the ice is evenly distributed and the texture is creamy yet icy.
Pour the Oreo slushie into glasses, letting it mound slightly for visual appeal.
Serve immediately with a straw or spoon, enjoying the crunchy, icy, chocolatey treat.