The drink features their mocha frappe base with a scoop of Oreo cookie pieces and cookies and cream-flavored syrup. You can expect it to be priced in line with their other Frappe beverages.
According to this Reddit thread, it has been spotted in Florida, Missouri and Washington (I haven't seen it here in California). In areas where the drink is not available, a suggestion was made to get something similar by ordering a Chocolate Chip Frappe with Oreo cookies instead of chocolate chips (you would be missing the syrup though).
I've heard that the Oreo Frappe might go national in July but I haven't been able to confirm it so we'll just have to wait and see.