His first solo exhibition took place at the Junge Generation Gallery in 1960. From 1964, Muehl concentrated on the realisation of his actionist work, with which he wanted to remove taboos from socially repressed aspects of human nature through the use of human bodies and the staging of sexuality, death and birth. Muehl is one of the participants in “Art and Revolution” on 7 June 1968 at the University of Vienna.

In 1972 he founded the Action Analytical Organization, the AAO Kommune, with headquarters in Friedrichshof, Burgenland.