The 3rd Battalion disembarked in Lisbon in November 1808. It became part of Arthur Wellesley, 1st Duke of Wellington's army and fought at many of the key battles including Badajoz in March 1812, Salamanca in July 1812, Vitoria in June 1813 and the Pyrenees in July 1813 before pursuing the French Army into France and fighting them at Nivelle in November 1813, Orthez in February 1814 and Toulouse in April 1814. The 3rd Battalion belonged to Cole's 4th Division throughout the war. At the Battle of Sorauren (Pyrenees), the 3rd/27th lost two officers and 41 men killed, nine officers and 195 men wounded, and seven men taken prisoner. At Toulouse, the unit lost two officers and 23 men killed, and five officers and 76 men wounded.