In January 1811 Howard joined the army in the Peninsula, being placed in command of a brigade of the first division in succession to Sir William Erskine (Wellington Supplementary Despatches, xiii. 544). In the following July he was transferred to the second division, which he commanded as senior officer under Lord Hill till August 1812. In November of that year he was selected to command the 1st brigade of guards in the first division, and was in entire command of that division under Sir John Hope from June 1813 to the end of the war. He was present at the battles of Fuentes de Oñoro, Arroyo de Molinos, and Almaraz, and was on the two latter occasions specially commended for gallantry in Lord Hill's despatches (Wellington Despatches, viii. 381–3, 388, ix. 184–5), and was thanked by the home government (Sidney, Life of Lord Hill, pp. 199–200). He took continuous part in the operations on the frontier, 1813–14, and received the medal and one clasp for Vitoria and the passage of the Nive. On the conclusion of the war he became Lieutenant-Governor of Portsmouth and General Officer Commanding South-West District. The duties of this post prevented his joining the army in Belgium, but after Waterloo he was placed in command of the first division of the British Army during the occupation of Paris, with the local rank of lieutenant-general.