anytime I have requested the OASIS from a Ford Dealer, they never charged me for it... Just go to the Service Desk and tell the service writer you had just purchased the car and want to have an OASIS run on it to see if there are any prior maintenance records and/or recalls, waranty work, etc done to it. He should be able to run it on the spot by using your VIN.
Sometimes it will list the original selling dealer, the date it was delivered when new, etc - as well as any prior Ford Service work (again, this will ONLY show if the vehicle was serviced at any Ford, Lincoln or Mercury Dealer - it will not show any secondary shop work outside of a Dealer).