Training exercises and patrolling occupied her until 27 May, when she lent fire support for the initial landings on Biak Island. From 31 May to 2 June 1944, she served as a fighter director and warning picket off Biak, and bombarded that island. "Gillespie" came under repeated air attacks, but escaped damage or casualties. Duties in New Guinean waters continued; 5–6 July she bombarded positions on the west coast of Noemfoor Island to speed the advance of the 6th Army toward the Namber Drone area, and 20 July her 5-inchers attacked Insomeken Point and Arimi Island on the east coast of Noemfoor following the initial landings.