In 1689 O'Gara was a member of the
Patriot Parliament where he represented the constituency of
County Sligo. During the
War of the Two Kings he was given command of a newly raised infantry regiment in the
Irish Army which took part in an expedition led by
Patrick Sarsfield to capture the Protestant-held town of
Sligo. In 1690 O'Gara commanded the Jacobite garrison at
Jamestown in
County Leitrim, repulsing an advance by a much larger force of Williamite troops under
James Douglas. In 1696 O'Gara became the proprietor of O'Gara's Dragoons. O'Gara served with his regiment at the decisive
Battle of Aughrim, which ended in Jacobite defeat. Following the
Treaty of Limerick, O'Gara acted as a hostage until it was clear the terms had been honoured. He then went into exile as a
Wild Geese, joining the
Irish Brigade of the French Army. He was an influential figure at the Jacobite court-in-exile at
Saint-Germain. In 1727 the exiled
James III awarded him a
baronetcy and he was styled by the Jacobites as '''Sir Oliver O'Gara''', but this was never recognised by the
Irish government in
Dublin. ==Marriage and issue==