Combine old-fashioned oats with your choice of milk in a mixing bowl or mason jar, stir until fully submerged and evenly coated.

Gently fold in crushed Oreos and, if using, Greek yogurt, mixing until well-blended and evenly distributed.

Cover with a lid or plastic wrap and place in the refrigerator, letting it chill for at least 4 hours or overnight.

Scoop into bowls or keep in jars, top with a dollop of whipped cream and additional Oreo crumbles for serving.