He was one of a family, of Huguenot origin, prominent in Dublin Methodism. His father James Beckett (1841-1915) and his uncle William Beckett (1843-1930) were building contractors who built the Methodist church in Rathgar, Dublin. They also built the National Library and the National Museum on either side of Leinster House in Dublin, and it was this undertaking that first inspired a love of architecture in James' son George.
George began practice in 1897. He was chiefly interested in ecclesiastical, domestic and industrial design and was probably happiest working on churches, of which he designed several for Methodist congregations, including: Dolphins Barn Church and School, Dublin (1899-1901); Roscrea Church and Lecture Hall (1901-2); Sutton Church (1903-4); Dun Laoghaire Church (1903-4; extended 1957); Portarlington Church (1904); Ringsend Church (1904); Roscommon Church (1904); Killarney Church (1907) and Manse (1909; completed 1913); Wesley College, Dublin, War Memorial Chapel (1927).
He married Edith Alice Park, daughter of the Rev Dr John Oliver Park (1845-1941) and one of their daughters, Primrose, married the distinguished, Irish Haitian Missionary, Rev H Ormond McConnell, for whom her father designed the Methodist Church in Port-au-Prince.
A leading member of the Civics Institute of Ireland, he had a significant influence in the preparation of the Dublin Civic Survey of 1925, which led ultimately to the programme of slum clearance in the city in the mid-20th century. He was President of the Royal Institute of the Architects of Ireland from 1932 to 1935.
William Beckett was the grandfather of the author and playwright Samuel Beckett, Nobel laureate in literature.