Edmund Barclay's career in Australian theatre was primarily in the area of radio, for which he wrote numerous plays and serials. The Australian Broadcasting Commission employed Barclay as a writer in 1933 under Lawrence H. Cecil, the head of drama production. The following year, while still at the ABC, Barclay and composer Varney Monk had their romantic musical, The Cedar Tree, staged in Melbourne under the auspices of F. W. Thring's EFFTEE productions. It played in Sydney the following year. Also involved in the creation of The Cedar Tree was Helen Barclay, who, along with Jock McLeod (and Varney Monk), provided the lyrics the music.
In 1934 Barclay co-wrote the screenplay (with Gayne Dexter) for Ken G. Hall's motion picture adaptation of The Silence of Dean Maitland. Three years later Barclay provided the story for Hall's Lovers And Luggers (1937), having adapted the narrative from the novel by Gurney Slade.
Barclay's contribution to Australian radio drama includes Murder In The Silo, Job (adapted from the bible story), Spoiled Darlings, The Man Who Liked Eclairs (with Joy Harper), His Excellency Governor Shirtsleeves, The Ridge and The River (adapted from T. A. G. Hungerford's novel) and As Ye Sow. Barclay also adapted into radio dramas many novels, including The Fortunes of Richard Mahony, The Idiot and Les Miserables. Among his collaborations, too, was the song 'Night in the Bush' (1933), with music by Alfred J Lawrence.