In 1806 the regiment returned to the United Kingdom. The following year, the regiment was deployed to Jersey in the Channel Islands for garrison duty. It was stationed there until 1808, when the 76th were deployed to Spain to take part in the Peninsular War.

In that campaign, the regiment fought at the Battle of La Corunna in January 1809, as part of the 2nd Division, under the command of Lieutenant-General Sir John Hope. The 76th fought with distinction in a battle that caused 800 casualties for the British and 1,500 for the French.

In that same year, the 76th were then involved in the disastrous expedition to the Low Countries. Some 39,000 troops landed at Walcheren, with the objectives of destroying the French fleet, believed to be at Flushing, and of assisting the Austrians who were now at war with France. Unfortunately, by the time the British forces had actually landed, the Austrians had been defeated. The British did capture their objective of Flushing, but the French fleet had already escaped, making their way to Antwerp. During the expedition, the 76th was part of the 3rd Division, which landed on Walcheren Island while other divisions landed on South Beveland Island. Over 4,000 men died in the expedition: only 106 of these in combat; the rest were taken by Walcheren Fever. Many thousands who took part in the expedition were still weakened by the illness despite returning to Britain. It was a truly disastrous campaign.

In 1813 the 76th returned to Spain, taking part in a number of actions in the closing months of the campaign. The Peninsular War was soon over though. The 76th were not to get any respite and were soon dispatched to take part in the British–American War: a war that had begun just a year before, in 1812.