In June 1797, Asgill was appointed brigadier-general on the Staff in Ireland. He was granted the rank of major-general on 1 January 1798, and was promoted Third Major of the 1st Foot Guards in November that year. In his service records, he states he "was very actively employed against the Rebels during the Rebellion in 1798 and received the repeated thanks of the Commander of the Forces and the Government for my Conduct and Service." General Sir Charles Asgill marched from Kilkenny and attacked and dispersed the rebels. Kathleen Toomey writes: "If the men of the Glengarry Fencibles had suffered from the ennui of inaction on Guernsey, the transfer to Ireland brought it to an abrupt end … Within the next few months, the regiment was kept on the march. In July [1798] they were in Kilkenny and Hacketstown; in August, they were part of Sir Charles Asgill's force in the Shlievenamon mountains prior to the attack on Callan."