In 1974 he was one of a group of Protestant clergymen who met with Provisional IRA officers in Feakle, County Clare in the 1970s to try to broker a peace after achieving a temporary ceasefire. The meeting was broken up by the Gardaí but the IRA officers had already left. He spent 22 years as superintendent of the Belfast Central Mission, from 1957 until 1979.
At Rev Gallagher's funeral in January 2000, Cardinal Cahal Daly, with whom Gallagher had jointly chaired a social issues group behind the Violence in Ireland report to the churches stated: "Not many people have been clear and steady beacons of light in the darkness of the last 30 years. Eric Gallagher was one ... [I]t was a privilege to work with him ... he took risks for peace."
Rev. Gallagher was the subject of Peacemaker, written by Dennis Cooke.