Here "Grainger" was assigned to the Logistics Support Group, Captain B. L. Austin, for the U.S. 7th Fleet as a replenishing ammunition ship. She continued this important job until 15 September when she got underway for the objective area in support of the landings at Inchon, one of the most successful amphibious operations in history. "Grainger" participated in the landings 16 September, and after landing her cargo remained in Inchon Harbor until 7 October, when she retired to Sasebo.