The Third Recruit Training Battalion is led by Lieutenant Colonel William C Berris and Sergeant Major David A. Cadd . Within 3rd RTBn., there are five companies: Co. I, Co. K, Co. L, Co. M, and Co. Q. Each company contains an average of six, 60- to 80-recruit platoons.

Third Battalion was initially formed on Aug. 7, 1940, and existed throughout World War II until it was deactivated on June 18, 1947. The battalion was reformed the following year and was used to train draftees from Aug. 2, 1948, to Jan. 8, 1949, when it was again disbanded.

In February 1949, the battalion was reactivated and it was used exclusively for the training of women Marines until May 7, 1954, when a separate women's battalion was formed, and male recruits and instructors from Fourth Recruit Training Battalion were designated as the Third Recruit Training Battalion.

On Feb. 28, 1955, the battalion was again deactivated, then reformed on Oct. 15, 1955, only to be temporarily closed on Oct. 25, 1957. Then in 1960, with the completion of the Depot's first brick recruit barracks, the battalion was re-established and has continued to serve the Marine Corps Recruit Depot.

To continue building upon its proud history, on April 7th 2008 the battalion resurrected Co. Q (Quebec
Company), a training company that hasn't been active in forty years. Co. Q has been added to the structure of the Recruit Training Regiment during significant periods of growth in the ranks of the Marine Corps, specifically during World War II and the war in Vietnam. Now, as the Corps grows to fight during the Long War on Terrorism, Co. Q has been formed to meet the national initiative train more recruits to swell the Corps' ranks by 2012.