For the next four months, "Bougainville" operated in a replenishment capability, supplying the Third Fleet's Fast Carrier Task Force with supplies, replacement aircraft, and munitions. She first supported Vice Admiral Marc Mitscher's carriers as they conducted operations in support of the landings on Iwo Jima. Upon the conclusion of said campaign, she providing aircraft to replace losses sustained in raids against the Japanese mainland, and she also provided support throughout the first six weeks of the Battle of Okinawa. During the Okinawa campaign, she had the task of providing replacement aircraft for both the escort carriers and the fleet carriers. Throughout her service as a replenishment carrier, she received supplies and additional aircraft from bases located within Eniwetok, Guam, and Ulithi in the Caroline Islands.