On 3 July 1863, he was appointed as a Member of the Queensland Legislative Council, and was a member without a portfolio of the first Ministry formed by his friend Sir Robert Herbert, the first Premier of Queensland, from July 1863 to February 1866, acting briefly as Attorney-General from 31 August 1865 to 11 September 1865.

[1] Robert Herbert established a farm in the Brisbane area and lived in the farmhouse with John Bramston.

When Charles Haley resigned as Member of the Queensland Legislative Assembly for Burnett, Bramston was elected in the resulting by-election on 3 April 1871.

The Governor hosted a wedding reception at Government House and the couple honeymooned in Sydney and Tasmania.

In June 1876 Bramston was appointed as Assistant Under Secretary of State in the Colonial Office, being employed on a mission to Berlin in connection with the Angra Pequena negotiations in July 1886, in which year he was created Companion of the Order of the Bath.

In October 1887, Bramston's death was announced in the Queensland newspapers, resulting in the publication of many obituaries.

In 1899 he was sent as Royal Commissioner in conjunction with Admiral Sir James Erskine to inquire into French treaty rights in Newfoundland.