Oxley was born in England in the early part of 1781. In his youth he entered the navy, saw active service in many parts of the world, and rose to the rank of Lieutenant. He came to Australia in January, 1812, and was appointed Surveyor-General in the Royal Navy. In 1804-05 he conducted a survey of Westernport on Bass Strait, among other duties in New South Wales and Van Diemen’s Land. He sailed to England in 1810 for a brief visit. In 1812 he was appointed Surveyor-General of New South Wales.
In April 1815 he was with Macquarie when Bathurst was founded, and in March 1817 he was instructed to take charge of an expedition to ascertain the course of the Lachlan River. He decided to take Evans with him on his expeditions and left in April 1817, following the Lachlan River westwards. After about 100kilometres the party left the river banks, turning south-west. They moved across country, passing through the area where Rankin Springs is now located. From here Oxley turned north-west, once more coming to the Laclan River.
Much of the country was found to be swampy, and on 9 May the way was barred by a huge marsh. Retracing their steps for some distance they then proceeded in a south-westerly direction, and on 20 May found themselves in very dry country. Hardly any water was available and what was found had to be boiled twice before it was drinkable. For the next five weeks dense scrubby country was constantly encountered and there was a great shortage of water. One of the horses died and another had to be shot. It rained several times but this gave them little water; Oxley says in his journal that the soil absorbed all the rain that fell like a sponge. They had travelled 1900 kilometres and found some excellent grazing lands. Oxley told Macquarie, however that the western rivers flowed into useless country. This comment greatly delayed further opening up of the far west.
Oxley’s next exploration began on 6 June 1818, again with George Evans as his deputy. The group headed north-west along the Macquarie, following Evans’ original trek. Oxley’s path was again frustrated by impenetrable marshes. The presence of these swamps led many people to think there was a great sea in the centre of the continent. Oxley then dispatched Evans across country to the north-east where Evans discovered the Castlereagh River. Reunited with Evans, Oxley led the expedition further north-east towards the Warrumbungle Ranges. Here they discovered the rich and fertile Liverpool Plains. They then turned east to cross the Great Dividing Range and descend to the coast, following the river Hastings to its mouth. Oxley named the area Port Macquarie. They then headed south along the coast of Newcastle.
By the 1820s it was decided there was a need for a new penal settlement to house the most difficult convicts. Governor Thomas Brisbane sent Oxley north by boat in search of a site in 1823. Having rounded Moreton Island, Oxley encountered two escaped convicts who had been living with Aborigines. The convicts showed him the mouth of a large river, which Oxley explored and named after Governor Brisbane. In 1824 the Moreton Bay settlement was established some distance up the Brisbane River.
Oxley was an excellent public servant and explorer. He became a well-known landowner near Bowral in the highlands south-west of Sydney. He was a director of the Bank of New South Wales (now Westpac) from 1821 to 1825 and he sat as a magistrate. Oxley later became a Governor Brisbane appointed him to the Legislative council in 1824.
As an explorer he was not afraid to take risks, but he knew how to manage the strength of both his horses and the members of his party. He never lost a man, though his own health suffered. He was unable to solve the riddle of the rivers, which appeared to lose themselves in marshes, but he added much valuable land to the known territory of his time. Oxley died in Sydney at 45 years of age.