He sold his farm to prospect for gold during the Coolgardie, Western Australia gold rush and then returned to Victoria to farm at Macarthur before becoming an organiser for the Australian Workers" Union (AWU) in western Victoria and the Riverina of New South Wales. McNeill contested the Victorian Legislative Assembly seat of Glenelg for Australian Labor Party in 1906. In 1908 he tried to farm in Roma, Queensland and then became an AWU organiser in Charleville.
From 1913 to 1922 he was secretary of the Victoria-Riverina branch of the AWU. On 2 March 1931, dissatisfaction with the economic performance of the Scullin Government and internal rivalries within the Labor Caucus resulted in the Caucus declaring all ministerial positions vacant and subsequently a new ministry was elected.
McNeill was elected to cabinet and was allocated the portfolios of Health and Repatriation. He kept these positions until the Scullin Government resigned on 6 January 1932.
He lost his parliamentary seat at the December 1931 general election. McNeill was the General President of the Australian Workers" Union from 1939 until his death in the Sydney suburb of Coogee of a coronary occlusion.