A former student of leading Sydney drama and elocution teachers, Stella Chapman and Douglas Ancelon, Harley Cohen enlisted in the Australian Imperial Forces (A.I.F.) in 1915. He first came to prominence as a songwriter and performer in 1916 when his song 'They Were There, There, There' was sung to much acclaim on the Tivoli circuit by Peter Dawson. Cohen had written the words to the song while recovering from wounds he received during the Lone Pine charge at Gallipoli. The most serious of these injuries had resulted in the loss of any eye. He also became a popular choice for several companies as the face and voice for their advertisements, including Dr Sheldon's New Discovery (coughs and cold remedy) and Heenzo's Essence.
By mid-1916, having become somewhat of a celebrity, Cohen began making appearances at various concerts and entertainments, sometimes in company with other returned servicemen. Later that year he joined several other wounded soldiers to form a variety troupe that eventually became the original Gallipoli Strollers. Identified in the Australian Variety Theatre Archive as the Gallipoli Strollers 1 so as to differentiate it from a Western Australian-based troupe which also operated around the same period, the Strollers toured the Australia states through until at least mid-1920. One of the troupe's feature performers, Cohen presented turns that often comprised his own original songs and monologues.
A number of Cohen's published songs are held by the Australian National Library. Among his last known works were 'The Old Town Rings With Gladness' (a tribute to all the mothers who had lost sons in the Second World War) and 'Because I Love Australia,' published in 1954.