A second battalion was raised in November 1803 but it solely served as a reinforcement pool and never left the United Kingdom. The 1st Battalion embarked for Copenhagen in August 1807 and took part in the Battle of Køge and then the Battle of Copenhagen later that month during the Gunboat War.
The regiment embarked for Portugal in July 1808 for service in the Peninsular War. It served under Lieutenant-General Sir John Moore at the Battle of Corunna in January 1809 and subsequent evacuation. The regiment was renamed as the 92nd Regiment of Foot in 1809. It then took part in the disastrous Walcheren Campaign in autumn 1809.
The regiment returned to Portugal in September 1810 to resume its service under General Viscount Wellesley in the Peninsular War. It saw action at the Battle of Fuentes de Oñoro in May 1811, the Second Siege of Badajoz in June 1811 and the Battle of Arroyo dos Molinos in October 1811 as well as the Battle of Almaraz in May 1812 and the Battle of Vitoria in June 1813. It then pursued the French Army into France and fought at the Battle of the Pyrenees in July 1813, the Battle of Nivelle in November 1813 and the Battle of the Nive in December 1813 as well as the Battle of Orthez in February 1814 and the Battle of Toulouse in April 1814.
The regiment embarked for the continent again in May 1815 for service in the Hundred Days campaign. The regiment had a key role in the Battle of Quatre Bras on 16 June 1815 as one of the regiments defending the disputed crossroads and which later halted a French attack with a bayonet charge. Two days later the regiment was in action again at the Battle of Waterloo. At an early stage, Napoleon's troops attacked the left of the Allied line, and the regiment was ordered to charge the leading French column. The regiment did so and the French column then broke in disorder. The horses of the Scots Greys passed through the regiment to get to the scattering French troops and press the advantage. At this point some members of the regiment clung to the stirrups of the passing Greys so that they could reach the French troops. Corporal Dickson of "F" Troop of the Scots Greys, reported: "They were all Gordons, and as we passed through them they shouted 'Go at them the Greys! Scotland for ever!' My blood thrilled at this and I clutched my sabre tighter. Many of them grasped our stirrups and in the fiercest excitement, dashed with us into the fight." After the battle, the regiment marched to Paris and then embarked for home in December 1815. After arriving in Edinburgh on 7 September 1816, it was cheered by a large crowd.