As a heavily armed destroyer leader, she took part in type-training, readiness cruises, and battle problems in the eastern Pacific and in the Caribbean operating area.

On 10 August McDougal transported President Roosevelt to and from HMS Prince of Wales during the only meeting of the two leaders on board the battleship.

The President and the Prime Minister completed formulation of the eight-point declaration, embodied in the Atlantic Charter, 12 August; thence, both British and American ships departed NS Argentia later that day.

While battling heavy seas off Cape of Good Hope, she received news of the Japanese attack on Pearl Harbor.

She patrolled the southeast Pacific westward to the Galápagos and Juan Fernández Islands and touched coastal ports in Ecuador, Peru, and Chile.

[1] She cruised to Casco Bay 11 to 15 September and began support duty with the Operational Development Force, Atlantic Fleet (TF 69).