In October 1802 Oxley was engaged in coastal survey work including an expedition to Western Port in 1804-05. In 1805 Governor King appointed him acting lieutenant in charge of the Buffalo, and in 1806 he commanded the Estramina on a trip to Van Diemen's Land. Next year he returned to England where, on 25 November, he was commissioned lieutenant. He came back to Sydney in November 1808 to take up an appointment as first lieutenant in HMS Porpoise, having sailed out as agent for the Transport Board in the convict ship Speke, in which he shipped goods worth £800 as an investment. He had obtained an order from the Colonial Office for a grant of 600 acres (240 ha) near the Nepean River, but Lieutenant-Governor Paterson granted him 1,000 acres (400 ha). Oxley had to surrender these in 1810, but Governor Macquarie granted him 600 acres (240 ha) near Camden which he increased in 1815 to 1,000 acres (400 ha) again. This he called Kirkham.
When Paterson allowed the deposed Governor Bligh to leave Sydney in Porpoise in March 1809 Oxley was aboard and sailed with Bligh to the Derwent. Next year he wrote a lengthy report on the settlements in Van Diemen's Land before sailing for England in Porpoise in May. In London he applied for the post of Naval Officer in Sydney, and then, after paying Charles Grimes to resign, according to John Macarthur, he twice sought that of surveyor-general. Oxley denied that he had been a partisan of Macarthur when Bligh was deposed, but his letters show that he was on very intimate terms with the rebel leader. In 1812 he became engaged to Elizabeth Macarthur; this was broken off when her father discovered the extent of Oxley's debts. By that time, through the influence of Macarthur's friend Walter Davidson, Oxley's second application for the surveyor-generalship had been successful. In 1811 he had retired from the navy, and in May 1812 sailed for Sydney in the Minstrel to take up his new duties.
John Oxley was born in 1783 at Kirkham Abbey near Westow in Yorkshire, Great Britain. In 1799, he entered the Royal Navy when he was aged 16 as a midshipman on the 'Venerable'. He travelled to Africa in October 1802 as master's mate of the naval vessel Buffalo, which carried out coastal surveying (including the survey of Western Port). In 1805 Oxley was promoted to second lieutenant. In 1806 he commanded the Estramina on a trip to Van Diemen's Land (now Tasmania). He returned to England in 1807 and was appointed first lieutenant of Porpoise, joining her in 1808. In 1809 Porpoise visited Van Diemen's Land, carrying as a passenger Governor William Bligh, who had been deposed in the Rum Rebellion.
Lachlan River expedition 
In March 1817 John Oxley was instructed to take charge of an expedition to explore and survey the course of the Lachlan River. He left Sydney on 6 April with George Evans as second-in-command, and Allan Cunningham as botanist. Evans had discovered a portion of the Lachlan River west of Bathurst in 1815. Oxley’s party reached Bathurst after a week, where they were briefly detained by bad weather. They reached the Lachlan River on 25 April 1817 and commenced to follow its course, with part of the stores being conveyed in boats. As the exploring party travelled westward the country surrounding the rising river was found to be increasingly inundated. On 12 May, west of the present township of Forbes, they found their progress impeded by an extensive marsh. After retracing their route for a short distance they then proceeded in a south-westerly direction, intending to travel overland to the southern Australian coastline. By the end of May the party found themselves in a dry scrubby country. Shortage of water and the death of two horses forced Oxley’s return to the Lachlan River. On 23 June the Lachlan River was reached: “we suddenly came upon the banks of the river… which we had quitted nearly five weeks before”. They followed the course of the Lachlan River for a fortnight. The party encountered much flooded country, and on 7 July Oxley recorded that "it was with infinite regret and pain that I was forced to come to the conclusion, that the interior of this vast country is a marsh and uninhabitable". Oxley resolved to turn back and after resting for two days Oxley’s party began to retrace their steps along the Lachlan River. They left the Lachlan up-stream of the present site of Lake Cargelligo and crossed to the Bogan River and then across to the upper waters of the Macquarie, which they followed back to Bathurst (arriving on 29 August 1817).
Macquarie River expedition 
Oxley travelled to Dubbo on 12 June 1818. He wrote that he had passed that day 'over a very beautiful country, thinly wooded and apparently safe from the highest floods...'
Later in 1818 Oxley and his men explored the Macquarie River at length before turning east. On 26 August 1818 they climbed a hill and saw before them rich, fertile land (Peel River), near the present site of Tamworth. Continuing further east they crossed the Great Dividing Range passing by the Apsley Falls on 13 September 1818 which he named the Bathurst Falls. He described it as “one of the most magnificent waterfalls we have seen”. He discovered and named the Arbuthnot Range, since renamed the Warrumbungle Range. Upon reaching the Hastings River they followed it to its mouth, discovering that it flowed into the sea at a spot which they named Port Macquarie.
Discovery of the Tweed River 
As Surveyor General, Oxley made a close examination of the Tweed River and Port Curtis, and sources connected that investigation, principally the manuscript journal kept by Oxley, and the published Narrative of John Uniaeke, who accompanied Oxley. The following is an extract from Oxley's notebook entry for 31 October 1823:
Fri.31 October At 3[PM] made sail intending to anchor to the South of Point Danger. At 5[PM] passed close to a Bold Headland [present-day Point Danger] about 3 Miles North of Pt. D. [Cook's Point Danger - Fingal Head] On the South Side of this headland we had the satisfaction to discover a considerable river with an apparent clear entrance. Hove on for the purpose of anchoring between the Island and the Main land [Fingal Head]. At ½ past 5 passing too close to the Island we shoaled our “water to 2 ½ fms but almost instantly deepened to 5 fms. Anchored under the lee of the Island in 7 fms sandy Bottom being tolerably sheltered from the SSE round by the w to NE - the distance between the Island and the Main is about 50 chains, the point of the Main as well as the Island composed of regular Basaltic Pillars. To the South extends a Sandy Beach of about 3 ½ miles ending in a low sandy Point off which brakers seem to extend about ¾ of a mile. Soundings between the Island and the Main and found the deepest water 6 fms in mid channel rather including to the Mainland. Observed the River from the Mast head take a SW direction running through a moderately elevated country towards the Base of Mt. Warning.
Monday 27 October 1823: The wind being fair, we immediately got under way, and continued our course to the northward till Friday afternoon, when it shifted, and came on to blow so hard, that we determind to run in shore and look out for anchorage; this we found under the lee of a small island off Point Danger (so named by Captain Cook), about a mile from the land. While running down for this place, we perceived the mouth of a large river about a mile and a half to the northward; and next morning at daylight the master was dispatched in the whale-boat to ascertain the possibility of taking the vessel into it. Shortly afterwards, Mr. Stirling and I landed on the island with our guns. The rocks which formed the base was evidently of volcanic origin: it was of dark colour, full of small holes and extremely hard, while on the western side many regular circular cavities, some of which were about four or five yards in diameter at top, and tapered down gradually towards the bottom, which was usually filled with round stones.
One of these holes, in particular, had a communication underneath with the sea, and at every returning surf threw up considerable quantities of water with a loud noise. The superincumbent rocks were basaltic, and those of a small rock to the N.W. of the island, as well as those of a bluff headland, immediately opposite on the main, were inferior only in extent to the Giant’s Causeway in the north of Ireland.
John Uniack also noted:
“The little island under which we lay received the name of Turtle Island, in gratitude for the abundant supply of that fish which we procured from it. We also gave the name of ‘Tweed’ to the river. The latitude of our anchorage is 28° 8' S. and its longitude 153° 31'”
Captain Phillip Parker King had previously surveyed that portion of the coast in the proximity of Point Danger, although adverse weather conditions prevented his examining that portion too closely. His observations, as recorded on 22 and 23 May 1819, are as follows:
22. The next evening, Mount Warning was seen from the deck, although we were at least seventy-eight miles from it. 23 On the 23d at noon, our latitude was 28°9' when the Mount bore S 58° W (Magnetic).
At sunset the wind died away; and, from the land in the vicinity of the mountain indicating every appearance of the existence of either a large sheet of water or an opening of consequence, I was induced to remain two days to examine the beach more narrowly; but, after beating about with a strong south-easterly current which prevented my tracing the beach to the northward of the Mount, and having only seen an inconsiderable opening that communicates by a shoal channel with a small lagoon at the back of the beach, I gave up the search; still without satisfying myself of the non-existence of an inlet, which, if there be one, probably communicates with the sea nearer to Point Danger.
Lieut Oxley has since (1823) discovered this to be the case, for he found a stream empting itself into the sea, by a bar harbour close to Point Danger. Lieutenant Oxley called it the Tweed.
In the Appendix to the second volume of that work, containing a description of the ports, islands and coast between Port Jackson and Breakesea Spit, the following description of the Tweed River confirms that Captain King clearly considered Point Danger to be the southernmost of the two points:
The Tweed is a river communicating with the sea by a bar, on which there is twelve feet of water, it is situated about a mile and a half to the north of a small island off Point Danger, which lies in latitude 28° 8'
Captain Henry Rous further examined the Tweed River in 1828, and incorrectly identified the present-day Point Danger, as the Point Danger of James Cook and recorded the name ‘Cook’s Island’ rather than ‘Turtle Island’ of Oxley [Rous named Oxley's Tweed the Clarance River]:
The River Clarance, or more properly the Tweed, discovered by Mr. Oxley, but not explored, is in lat. 28° 9', long. 153° 34' bearing N.W.½ W. from Turtle Island distant 2 ½ miles - it is situated to the southward of a Bluff Head, connected with the Main by a flat sandy Isthmus, 250 yards wide from high water mark forming a boundary to the river on one side, and to capacious bay to the northward - affording good anchorage and shelter from East Southerly to North….There is a small river about 10 miles NW by W from the *north bluff of Point Danger inaccessible for boats.
Oxley's 1823 expedition to Port Curtis and Moreton Bay 
Oxley sailed northwards from the Tweed Area in the Mermaid to explore Port Curtis (the site of Gladstone) and Moreton Bay. He continued to explore the region, which is now known as South East Queensland. With the assistance of some shipwrecked sailors he discovered and named the Brisbane River, the site of the city of Brisbane. A monument was built at North Quay in 1924 to commemorate the site of his landing in Brisbane.
Governor Lachlan Macquarie granted him 600 acres (240 ha) near Camden in 1810, which he increased to 1,000 acres (400 ha) in 1815. He named this property Kirkham and raised and bred sheep. He was also briefly a director of the Bank of New South Wales. He was one of five members of the original 1824 New South Wales Legislative Council, but was not reappointed when the Council was reconstituted in 1825.
Personal life 
In August 1822, Oxley married Emma Norton (1798–1885), the youngest sister of James Norton who had followed her brother out to New South Wales from Sussex after he had established himself as an attorney in the colony.
Oxley and Emma Norton had two sons. The elder, John Norton Oxley became a Member of the Legislative Assembly, representing the Western Division of Camden in the first Parliament after the establishment of responsible government in 1856. He sponsored the Broad Gauge Act which encouraged the use of wagons with broad wheels instead of narrow-tired drays in order to cause less wear on public roads; this measure made him unpopular with the farmers and carriers in his electorate and he lost his seat. The younger son, Henry Oxley, also became a Member of the Legislative Assembly, representing the Electoral district of Camden between 1859 and 1860.
Oxley also had two daughters out of wedlock before his marriage: one with Charlotte Thorpe and another with Elizabeth Marnon.
Oxley's statue, from circa 1891, can be found in a niche on the Bridge Street facade of the Department of Lands building, in Sydney. To celebrate the centenary of Oxley's discovery of Brisbane, in 1924 a statue was erected in his honour. In 1976, Oxley was honoured on a postage stamp bearing his portrait issued by Australia Post. In 2012 a metal silhouette of Oxley was unveiled in Kirkham.
Oxley has been honoured through the naming of a large number of places and facilities in Australia, including:
- electoral districts in New South Wales and Queensland including:
- John Oxley Drive, a road in Frenchs Forest
- John Oxley Library, part of the State Library of Queensland, is dedicated to preserving and making available Queensland's documentary history
- John Oxley Memorial Hospital (now demolished), in Wacol, Queensland
- John Oxley Village, an on-campus residence of the Charles Sturt University Bathurst campus, colloquially known as "JOV" to students, and birthplace of the Village Fair music festival.
- Oxley, a town in New South Wales
- Oxley, a suburb in the Australian Capital Territory
- Oxley, a suburb in Queensland
- Oxley Creek, a creek in Queensland
- Oxley High School in Tamworth
- Oxley Highway, in New South Wales
- Oxley Island, located on the north coast of New South Wales
- Oxley Park and Oxley Vale, both suburbs in New South Wales
- Oxley's Plains, on which the Oxley township grew in north-east Victoria, was named by Hume and Hovell after John Oxley during their exploration from the Yass Plains to Port Phillip in 1824.
- Oxley Wild Rivers National Park
- "Mr John Joseph William Molesworth OXLEY (1785 - 1828)". Parliament of New South Wales. Retrieved 20 February 2013.
- "Family Notices.". The Sydney Gazette and New South Wales Advertiser (NSW : 1803 - 1842) (NSW: National Library of Australia). 28 May 1828. p. 3. Retrieved 4 November 2012.
- "TO-DAY'S YESTERDAY'S.". The Courier-Mail (Brisbane, Qld. : 1933 - 1954) (Brisbane, Qld.: National Library of Australia). 25 May 1934. p. 12. Retrieved 4 November 2012.
- E. W. Dunlop, "Oxley, John Joseph William Molesworth (1784–1828)", Australian Dictionary of Biography, National Centre of Biography, Australian National University, accessed 16 September 2011.
- "Sketcher.". The Queenslander (Brisbane, Qld. : 1866 - 1939) (Brisbane, Qld.: National Library of Australia). 2 June 1923. p. 11. Retrieved 29 April 2012.
- Serle, 1949.
- Oxley, John. "Journal of an Expedition in Australia – Part 1". Journals of Two Expeditions into the Interior of New South Wales.
- Oxley, John (31 October 1823). Notebook. Archives Office of New South Wales. Unknown parameter
- Uniack, John (1825). "John Uniack's first-hand account of that experdition entitled Narrative of Mr. Oxly’s Expedition To Survey Port Curtis and Moreton Bay With a View to form Convict Establishment There". In Pusuance of the Recommendation of the Commissioner of Ineuiry (Barron Field’s Geographical Memoirs on New South Wales).
- Field. Geographical Memoirs. pp. 33–34.
- Field. Geographical Memoirs. pp. 40–41.
- King, Phillip Parker (1827). Narrative of a Survey of Intertropical and Western Coast of Australia Performed between the years 1818 and 1822 1. London: Murry. pp. 178–179.
- King. Narrative of a Survey 2. p. 257.
- Rous, Henry (1828). Description of the River Clarance. Wilton’s Australian Quartly Journal. pp. 352–355.
- "Mr John Norton OXLEY (1824 - 1891)". Former Members Index A-Z. Parliament of New South Wales. 15 September 2008. Retrieved 30 January 2013.
- "Mr Henry Molesworth OXLEY (1826 - 1867)". Former Members Index A-Z. Parliament of New South Wales. 15 September 2008. Retrieved 30 January 2013.
- "The Late Mrs Emma Oxley". The Sydney Morning Herald (NSW : 1842 - 1954) (National Library of Australia). 18 April 1885. p. 8. Retrieved 17 September 2011.
- "Chronological Memoranda". The Sydney Morning Herald (NSW : 1842 - 1954) (National Library of Australia). 25 December 1857. p. 8. Retrieved 4 November 2012.
- "Statue of John Oxley". Public Art Around the World. GlobeVista. 2007. Retrieved 30 January 2013.
- "Timeline of State Library of Queensland history". State Library of Queensland. Queensland Government. 2012. Retrieved 30 January 2013.
- "Unveiling of a metal cut-out silhouette of John Oxley". Camden-Narellan Advertiser (Australia). 31 October 2012. Retrieved 30 January 2013.
- "Accomodation On Campus Bathurst". Charles Sturt University.
Further reading 
Johnson, Richard, The Search for the Inland Sea: John Oxley, Explorer, 1783-1828, Melbourne University Press, 2001.
- Works by John Oxley at Project Gutenberg
- Serle, Percival (1949). "Oxley, John". Dictionary of Australian Biography. Sydney: Angus and Robertson.
- Journals of Two Expeditions into the Interior of New South Wales, undertaken by order of the British government in the years 1817-18
- Australian Dictionary of Biography Online
- The Allan Cunningham Project, Allan Cunningham, botanist explorer 1791-1839, accompanied John Oxley on his journey along the Lachlan River in 1817
- John Oxley Library, a part of the State Library of Queensland