She commenced her own practice at The Mansions in George Street in 1893, making house calls in her horse and sulky initially, a bicycle and then in her much-loved motorcar.

[1] During World War I, Cooper volunteered with the Scottish Women's Hospital Service after was she was turned down by the Australian Army as female doctors were not wanted.

She served on the front line in France, Macedonia and Serbia and was in charge of the ambulance division, with all female drivers (including her friend Mary Josephine Bedford).

Operating in tents close to the front line, Cooper was later awarded the Order of St Sava from the Serbian King for her wartime efforts.

[11] In 2020, the State Library of Queensland produced an episode on Lilian Cooper and her life achievements for their Dangerous Women Podcast series.