"O'Brien" was retained at Pago Pago for local escort work. On 26 May, she supported the occupation of Wallis Island, previously taken over by the Free French, and then she joined the auxiliary vessel on 19 June for the return voyage to Pearl Harbor. Operating out of Pearl Harbor, the ship performed escort duty and acted as patrol and plane guard. She got underway on 17 August with Task Force 17 (TF 17) to reinforce the South Pacific Force, screening the tanker .