After the U.S. entered World War I on 6 April 1917, "Parker" was selected for overseas duty. She sailed on 17 June as an escort for the fourth group of the first American convoy, which carried units of the American Expeditionary Force. The convoy consisted of United States Army transports , , , and ; U.S. Navy transport ; and oiler . The escorts — in addition to "Parker" — were the cruisers , and destroyers , , and . The group departed from New York for Brest, France, steaming at an pace. A thwarted submarine attack on the first convoy group, and reports of heavy submarine activity off of Brest, resulted in a change in the convoy's destination to Saint-Nazaire where the convoy arrived 2 July.