The regiment was given a county designation, becoming the 77th (East Middlesex) Regiment of Foot in 1807. It took part in the disastrous Walcheren Campaign in autumn 1809 and, having been granted permission to bear the plumes and motto of the Prince of Wales as a badge in commemoration of twenty years service in India in February 1810, it embarked for Spain in June 1811 for service in the Peninsular War. It saw action at the Battle of El Bodón in September 1811, the siege of Ciudad Rodrigo in January 1812 and the siege of Badajoz in March 1812. The regiment then fought at the Battle of Bayonne in April 1814 before returning home in August 1814.