According to German news magazine Focus, Kušej belongs to the ten most important theatre directors who have emerged in the German-speaking world since the millennium.

[2] Born into the Slovene-speaking minority in the Austrian state of Carinthia he studied German, Literature and Sport Sciences at the University of Graz from 1979–82.

He received the Gertrud Eysoldt Prize for young directors for his version of Intrigue and Love by Friedrich Schiller which he had directed earlier that year at Stadttheater Klagenfurt in Austria, and which had produced a major scandal with audiences leaving the theatre within the first few minutes.

Towards the end of his time as resident director in Stuttgart he also worked at the Burgtheater in Vienna and at Thalia Theater in Hamburg.

In 1999, he was invited to the Berliner Theatertreffen festival with his Hamburg production of Tales from the Vienna Woods by Ödön von Horváth.