In 1958 he followed an invitation by Bertold Brecht to his Berliner Ensemble in East Germany, and worked also for Deutscher Fernsehfunk directing television plays.

[1][3] He received an offer from the Stadttheater Klagenfurt already while studying, and directed there in March 1948 Das Haus in Montevideo by Curt Goetz.

[3] He then had engagements at the newly opened Stadttheater St. Pölten and later at the Tyrolean State Theatre in Innsbruck,[1] where he played roles such as Franz Moor in Schiller's Die Räuber.

In 1956 Klingenberg was invited by Bertold Brecht for his Berliner Ensemble in East Germany,[4] to work on the world premiere of his Die Tage der Commune.

[4][7] He introduced plays by authors such as Thomas Bernhard whose Die Jagdgesellschaft [de] caused controversies in 1974,[6] Harold Pinter and Tom Stoppard to the house repertoire.

[4] He directed there Hebbel's Judith with Rolf Boysen [de] as Holofernes in 1973, Grillparzer's König Ottokars Glück und Ende in 1976 with Heinz Reincke in the title role, often with political analogies to a divided Europe.

[6] Klingenberg returned to the Schauspielhaus Zürich where he was theatre manager from 1977 to 1982,[1] where he directed Schillers Wilhelm Tell and Dürrenmatt's Romulus der Große.