This subseries consists of correspondence, promotional materials, bulletins, and notes about several Irish and Irish American cultural, charitable, education, and academic organizations of which O'Malley was an officer or member, including the American Irish Foundation, An Taisce (National Trust of Ireland), and the Canadian Association for Irish Studies. Of particular note are folders concerning the New York Shakespeare Festival's 1973 memorial to Jack MacGrowan and the 1975 donation of the James A. Healy Collection to the Sligo Museum and Library.

This subseries consists of materials related to the activities of the American Irish Historical Society during the period in which O'Malley was directly involved in the organization (1968-1981). Materials relate to the society's library and art collection. The subseries also includes an index to the Journal of the American Irish Historical Society drafted by O'Malley in 1974.

This subseries consists of materials concerning the Irish American Cultural Institute (founded in St. Paul, Minnesota in 1962) during the period in which O'Malley was directly involved in the organization (1967-1981). Materials relate to the organization's Irish Fortnight Series of lectures in New York which brought over speakers from Ireland to discuss a variety of cultural topics.

This subseries consists of materials concerning the Irish American National Bicentennial Committee (1973-1978), established to involve Irish Americans in the activities surrounding the 200th anniversary of the founding of the United States. The organization had chapters in several states through which it sponsored events and projects, such as the participation of the Irish tall ship Creidne in Operation Sail. Of note in this subseries is O'Malley's "Planning Guide to the Irish American Bicentennial Celebration in Your Community" (1975) and an index card file of select people in the Irish American community living on the East Coast.

The 2016 accretion includes correspondence between O'Malley and state chapters of the Committee and other Irish and Irish American organizations, research files on topics related to the work of the Committee, and files documenting the work of the Art Committee and the Research Committee.

This subseries consists of materials concerning O'Malley's membership in the New York branch of the National University of Ireland Club during the period of 1968-1981.

This subseries contains materials documenting O'Malley's involvement in NYU's Glucksman Ireland House (GIH) during the years 1999-2014. Materials include correspondence with GIH donors, Irish Studies course syllabi and curriculum planning documentation, promotional material such as brochures and postcards, correspondence and memoranda concerning film and lecture events, correspondence concerning potential archival collections for the Archives of Irish America, and materials concerning the activities of the GIH Advisory Board, including correspondence, memoranda, and meeting minutes.

This subseries documents O'Malley's involvement in the American Ireland Fund from its incorporation in 1976 to 2014 and his membership in one of its predecessors, the American Irish Foundation from 1965 to 1977. The bulk of the records document O'Malley's service as secretary from 1976 to 1981 and as a member of the Advisory Committee from 1984 to 1988. Materials include correspondence; board agenda and minutes; the American Ireland Fund's publication, Connections, later titles Connect; bylaws, financial reports, newspaper clippings, and ephemera.

This subseries documents O'Malley's involvement in the Irish Georgian Society from 1977 to 2011. The bulk of the records documents his service as a member of the Board of Directors from 1977 to 2005 and include correspondence with other directors, including Desmond Guinness, the founder of the Society; financial material; reports on funding and buildings nominated for conservation; newsletters; and board agenda and minutes.

This series documents O'Malley's participation in the O'Malley Clan Association between 1959 and 2011, including his tenure as Tanaiste of the Clan in 1993 and as Chieftain in 1994. The records include correspondence, research files, ephemera, and financial documents. The bulk of the records document the planning of the annual O'Malley Clan Rallies in County Mayo, Ireland. Other records include family trees and newspaper clippings on members of the Association in the research files and correspondence with other members of the Association regarding clan history, Rallies, and membership issues.

This subseries documents O'Malley's participation in the Granuaile Trust of the O'Malley Clan in Ireland and The Granuaile Trust Foundation in the United States between 1986 and 2000. The material for the Granuaile Trust of the O'Malley Clan documents his work as a member of the board of trustees from 1986 to 2000 and the material for the The Granuaile Trust Foundation documents his work to establish the Foundation and make it a successful organization.

This subseries consists of correspondence, memoranda, publications, research notes, and press releases related to the regular activities and the functions of the ACUJ.

This subseries consists of materials concerning the ACUJ's participation in a Congressional hearing before the House of Representatives' Foreign Affairs Subcommittee held in the aftermath of the Bloody Sunday shootings in 1972. Materials include correspondence, newsletters, press releases, research notes, transcripts of statements, and information concerning the Kennedy-Ribicoff Resolutions on Violence in Northern Ireland.

This subseries consists of research materials used to inform the ACUJ's testimony in the Congressional hearing before the House of Representatives' Foreign Affairs Subcommittee held in the aftermath of the Bloody Sunday shootings in 1972. Included are extensive newspaper clippings from Irish and American newspapers and magazines, transcripts of the Parliament of Northern Ireland debates (1971-1972), and statements made by individuals to the Association for Legal Justice in Belfast that same winter. Of note are the 1972 platforms of the American Democratic and Republican political parties with respect to the situation in Northern Ireland, position papers released by the British and Irish governments, the Amnesty International Report of an Enquiry into Allegations of Ill-Treatment in Northern Ireland, and press coverage concerning St. Patrick's Day in the wake of the 1972 Congressional hearing.