"Cowell" cleared Boston, Massachusetts, 3 May 1919, to take station at Trepassey Bay, Newfoundland, first stopping point for the Navy seaplanes which that month began the historic first aerial crossing of the Atlantic. After patrolling her station, she returned to Boston 22 May to prepare for European service, and on 30 June sailed from New York to join the American naval force in the Adriatic. Here she served as dispatch ship for the Allied Peace Commission, and as station ship at Croatian (then in Kingdom of Serbs, Croats and Slovenes ports of Rijeka, Split, and Trogir, in turn until 23 October, when she cleared for home.