The 1st battalion was reformed and embarked for Portugal in June 1808 for service in the Peninsular War. Renamed the 71st (Glasgow Highland) Regiment of Foot later that month, it saw action at the Battle of Roliça in August 1808, the Battle of Vimeiro later that month and Battle of Corunna in January 1809 before being evacuated from the Peninsula. In March 1809 it became a light infantry regiment, and the regiment next took part in the disastrous Walcheren Campaign in autumn 1809 before returning home and being renamed the 71st (Highland) Regiment of Foot (Light Infantry) in spring 1810.