In 1787, he was made Major and joined the 60th briefly before returning to the 51st. In 1791 his unit was assigned to the Mediterranean and he was involved in campaigning in the invasion of Corsica and was wounded at Calvi. He was given a Colonelcy and became Adjutant-General to Sir Charles Stuart. Friction between Moore and the new British viceroy of Corsica led to his recall and posting to the West Indies under Sir Ralph Abercromby in 1796. Moore played a leading role in the British recapture of St. Lucia, which at the time was under the nominal control of the French as a result of a successful invasion by French Republican administrator Victor Hugues. During the campaign, Moore retook Fort Charlotte with the 27th Inniskilling Fusiliers after two days of bitter fighting. The regiment was honoured for their actions in capturing the fort by having their regimental colour displayed on the flagstaff of the captured fortress at Morne Fortune for an hour, before being hauled down and replaced by the British flag. Upon the capture of the fort, Abercromby departed the island, placing Moore in charge of the British garrison. Moore remained at this post until falling with yellow fever, upon which he was repatriated to Britain.