Koukias is one of Australia's most prolific composers in the genre of opera and music theatre. His avant-garde approach to the presentation of opera has resulted in hybrid opera such as Days and Nights with Christ, To Traverse Water, MIKROVION (Small Life 36 Images in a Phantom Flux of Life), The Divine Kiss and Tesla - Lightning in His Hand. His works range from large scale site - specific to gallery pieces. His compositions written predominantly for orchestra/voice or for various ensemble line-ups, have been always remarkable for their peculiar, mesmerising atmosphere created by temporal, spatial and sound effects. Into his recent works, exotic flavours have been introduced through Eastern timbres and melody-design. His work Prayer Bells - Pentekostarion, which draws on traditions of religious chant, was commissioned for the Melbourne Federation Festival in 2001 and has toured extensively with US and European premieres taking place in 2010 and 2011.
Constantine has been the recipient of numerous international commissions and awards. In 2004 he was awarded a Churchill Fellowship. Within a Prayer at Lamplighting was commissioned by the China National Symphony Orchestra Australian Tour, to commemorate thirty years of diplomatic ties with China. In 1997 his Incantation II for soprano and digital delay won the International Valentino Bucchi Vocal Prize in Rome.
Since the formation of his company IHOS in 1990, he has created and presented five full scale operas, nine music theatre works and commissioned nationally 29 short to 50 minute Laboratory works for his IHOS Young Singers Laboratory Program. Constantine Koukias composed for Chrissie Parrott's work Racing Heart/Hummingbird, performed in Tasdance's Heart Matters production in 2010.