While the Navy and Marine Corps Overseas Service Ribbon (OSR), authorized by Secretary of the Navy John Lehman in September, 1986, can be awarded to active-duty and reserve officers and enlisted personnel in the Navy and active-duty members of the Marine Corps, its eligibility criteria varies between the services. When determining if an individual is eligible, the criteria of the service to which the candidate is assigned is employed.
Active-duty personnel in the Navy or Marine Corps who accumulate 12 months of duty time at an overseas, shore-based duty station are considered eligible for the award (the duty time can either be consecutive or cumulative). The rules are a bit more complex for Reserve personnel, with a minimum of 30 consecutive or 45 cumulative days of service at a qualifying duty station; days that are designed as Inactive Duty for Training count as just a half day of duty time, and time spent in traveling does not count at all.
The regulations for Navy Reserve Personnel were further modified following the terrorist attacks of September 11, 2001 because of the need for rapid operational deployment. Beginning on that date, Navy Reserve personnel can earn their first OSR under the Reserve requirements mentioned above, but any subsequent awards will be based on active-duty service requirements. (Navy Reservists who live overseas must accumulate their qualifying days of duty service in a billet with an established Navy Reserve Unit.)
Whether active-duty or reserve, Navy or Marine Corps personnel who are serving with Marine Corps operating forces that have been mobilized in support of a specific operation or contingency are not eligible for the Overseas Service Ribbon. Active-duty personnel serving on board Continental U.S.-based, deploying ships, squadrons, units, or with the Marine
Corps operating forces are not eligible for the award. Note that subsequent to 1 October 1999, personnel who have been assigned to overseas Navy commands may receive both the OSR and the Sea Service Deployment ribbon provided all the eligibility requirements for both decorations are met. The exception to this is Naval Reservists; they cannot use the same period of time as forming the basis of their eligibility for both the Naval Reserve Sea Service Ribbon and the Overseas Service Ribbon.