As co-founder of the group Theater Angelus Novus he is first of all known for his experimental approach to texts by Heiner Müller, Bertolt Brecht, Homer and Greek dramas.
Out of this project arose the group TheaterAngelusNovus which focused on a continuous reflection of theatrical aspects (“Selbstverständigung”) rather than producing small packages of ready made performances that could be consumed in a traditional setting.
In 1998 Josef Szeiler co-founded the group Theaterkombinat Wien, which in 1999-2000 produced MassakerMykene at the abattoir St. Marx in Vienna, working with Bertolt Brecht’s Fatzer Fragment and The Oresteia by Aeschylus.
An important aspect of Szeiler's approach to the theatre is his use of time, based on the understanding that the usual rhythm of theatrical production (2–3 months of preparation followed by 2 hour evening performances) serves more to confirm the social status quo than helping to raise questions.
Other than with the musical choir, which is usually directed by a central conductor, the chorus is envisaged here as a homogeneous organism, which finds its position, rhythm and movement in spontaneous response to the given situation.
The approach in concrete productions was likened to the ones of soccer players who practice positions and movements in training which may or may not work the same way in a match and rely on the capability to adapt to situations at hand.