He became involved in the union movement on the Eastern Goldfields, and entered parliament at the 1905 state election, winning the seat of Boulder (which he retained for the rest of his life).

He spent some time gold mining at Steiglitz, Victoria and then in New South Wales, and was later construction foreman of the Greater Melbourne Sewage Company at Northcote.

He worked in the mines of the Perseverance Goldmining Company for around a year, becoming a member of the Boulder branch of the Amalgamated Workers' Association, and vice-president of the Goldfields Trades and Labour Council.

Collier retained the leadership of the Labor party throughout the Liberal and nationalist governments of Frank Wilson, Henry Lefroy, Hal Colebatch and James Mitchell.

On 17 April 1924, the Labor party had a landslide election victory, and Collier became Premier, Treasurer and Minister for Forests.

In addition, both the annual wheat harvest and the area under crop more than doubled, workers' compensation benefits and entitlements were increased, and industrial safety requirements were made more stringent.

A state basic wage award was also introduced, together with regulations on the working conditions of timber workers, coal miners, and employees in other designated industries.

In addition, although the Legislative Council rejected the introduction of a 44-hour workweek and preference to unionists, the Collier government was able to introduce both measures for most of its own employees through the use of administrative action.

Victor Courtney (1956) describes him as "the only person Labor [sic] produced in State politics who could fairly claim to have approached statesmanship".