In January 1707, Erle took part in an expedition to Spain, fighting in the Battle of Almanza on 23 April 1707 — some reports state that he lost his right hand. and remained there until September. During the debate on the deficiency of English troops at Almanza, Erle defended Lord Galway, the commander, in the Commons on 24 February 1708. At the 1708 general election, he was returned for Wareham and Portsmouth and sat as Whig MP for Wareham. Erle was then told that he was to be commander-in-chief of an attack on the French coast. He was annoyed with the posting, especially as his pay had been stopped when he came back from Spain. Erle was awarded arrears of pay and given a further £1,500 in consideration of his services. The expedition was late in starting and the plan to land at St Valery to capture Abbeville was abandoned. The force eventually landed at Ostend and set up an outpost at Leffingham, which fell to the French without a fight on 16 October 1708. In spite of the failure, when Erle returned home in December 1708, he was appointed commander-in-chief of land forces in England. He voted for the naturalization of the Palatines in 1709, and for the impeachment of Dr Sacheverell in 1710.