He then served as executive officer of the Marine Detachment aboard USS Kennedy (CV 67), then as commanding officer of the Marine Detachment aboard the USS Forrestal.

As a lieutenant colonel, Osterman was the commanding officer of the 1st Battalion, 3rd Marines and participated in support of Operation Enduring Freedom.

This was followed by a joint tour as an instructor and as the chief of staff, NATO School, Oberammergau, Germany, where he was responsible for training support to some 54 nations.

Following his promotion to colonel, Osterman assumed command of the 25th Marine Regiment in 2004 and deployed to Iraq as an adviser to the Iraqi army.

Osterman's joint assignments include the International Security Assistance Force Joint Command Deputy Chief of Staff of Operations, Afghanistan, and as Instructor and Chief of Staff at the NATO School, Oberammergau, Germany.