Read the answer in "Black-and-White"
In Daf HaKashrus 22.9 (August 2014) the OU had an update on Oreos.
At the present time, most varieties of Oreo Cookies contain dairy ingredients, with three notable exceptions. Original Oreo Sandwich Cookies, Oreo Double Stuf Sandwich Cookies and Mini Original Oreo Sandwich Cookies do not contain dairy ingredients, though they are manufactured on dairy equipment. The equipment is not necessarily cleaned before the production of these three cookies, and there may be a small amount of dairy residue present. Nonetheless, the dairy component would be minimal, and from a Halachic perspective, the dairy residue is nullified (botel bishishim) and of no consequence.
The bottom line of all this is that these three cookies may be consumed after meat and poultry, but not simultaneously.
Please bear in mind that the manufacturer may choose in the future to reformulate these products and add dairy ingredients. Since these products already bear OUD symbols, formulation changes would not be reflected in the OUD logo.
As such, we recommend that consumers check regularly with our office to confirm the status of these items.