Lascelles and his regiment were posted to Nova Scotia in 1750; conflict between British and French settlers resulted in a series of clashes known as Father Le Loutre's War, the most significant being the June 1755 Battle of Fort Beauséjour. He remained in North America for at least part of the Seven Years' War, the 47th forming part of the force commanded by James Wolfe that captured Louisbourg in 1758. He was promoted Lieutenant-General shortly afterwards, and the 47th then fought at the capture of Quebec in 1759, where Wolfe was killed, and Sainte-Foy in 1760, before returning to Britain when the war ended in 1763.