He was the son of Cornthwaite Hector Rason (Snr), a Royal Navy surgeon who was the medical officer at York, Western Australia, in 1866 and 1867.

In July 1889, while already a member of the Western Australian Legislative Council, he became the inaugural president of the newly-formed Stock Exchange of Perth.

In 1897 he was elected to the Western Australian Legislative Assembly seat of South Murchison, sitting as a supporter of Sir John Forrest's government.

When George Leake formed his second government in December 1901, Rason was appointed minister for works, holding responsibility for administration of the Coolgardie Water Scheme.

Like Daglish, Rason did not have a majority of support, but he was granted an early dissolution in October, and easily won the subsequent general election.

In May 1906 he appointed himself as Agent General for Western Australia in London before resigning as premier to take up the post, an action which drew strong criticism.