George William Herschel Maclear was the eldest son of Thomas Maclear*, astronomer in charge of the Royal Observatory, Cape of Good Hope, and his wife Mary (born Pearse). His second and third given names commemorate the astronomer William Herschel, whose son John F.W. Hershcel*, astronomer and friend of Thomas, was at the Cape when George was born. In 1870 George married Sophia Johanna Ansdell Laing, with whom he had about three sons and three daughters.
In June 1852 George was appointed by his father as second assistant (from 1872 second class assistant) at the Royal Observatory, succeeding Reverend George F. Childe*. A paper by him, "Right ascensions and north polar distances of comet II, 1861" was included with contributions by his father in Memoirs of the Royal Astronomical Society (No. 32, 1863). Four years later he published "On the meteor shower of 12-14 November 1866" in the Monthly Notices of the Astronomical Society of London (Vol. 27, pp. 65-75), followed by further contributions on the same topic during the next two years (Vol. 28, pp. 52-53; Vol. 29, pp. 233-236).
Maclear continued in his post under Edward J. Stone* (1870-1879). In December 1872 the first assistant, William Mann*, retired on grounds of ill health. Stone did not promote George Maclear, among others because he lacked a comprehensive mathematical background, and selected W.H. Finlay* instead. George next served under Dr David Gill* from 1879 and during the 1880's was elected a Fellow of the Royal Astronomical Society. He became unfit for duty as a result of severe illness in April 1892 and finally retired on pension at the end of June 1893.
George Maclear (like his father) was a member of the Cape of Good Hope Meteorological Commission from 1868 or 1869 and served continuously until 1893.