The regiment left its winter quarters in February 1691 and immediately saw action, forming part of a combined force of infantry and cavalry that engaged a 2,000-strong Catholic force near Streamstown and forced it to retreat; the role that the regiment played in this action led to Leveson being promoted to Brigadier-General. In May, the majority of the Williamite army moved north and besieged the town of Athlone, which fell after eleven days, but the regiment took no part in the siege, having been ordered to encamp in the county of Mullingar. At the beginning of July, the regiment formed part of the 12,000-strong Williamite army that defeated an 8,000-strong Catholic army during the Battle of Aughrim, taking part in a massed cavalry charge that breached the Catholic positions around the village of Aughrim. The Battle of Aughrim was a decisive victory for King William, with a number of leading Catholic generals being killed, and the Williamite forces pressed their advantage; they forced the surrender of Galway on 20 July and then began a second siege of Limerick in August. The regiment did not take part directly in the siege, instead being detached in late August and ordered to advance south-west into Kerry to reconnoitre and harass Catholic forces in the area around Limerick. On 2 September, the regiment ambushed and routed two regiments of Catholic cavalry, and several days later subdued a number of Catholic garrisons between Cork and Limerick. The regiment inflicted a number of casualties, but more importantly captured thousands of cattle and oxen; one contemporary source states that the majority of the army's provisions for the siege of Limerick were provided by the regiment. On 22 September, Limerick fell to the Williamite forces, effectively ending the conflict in Ireland; the regiment was withdrawn to its winter quarters and was then transported to England in the spring of 1692.