For the wave of ecological consciousness that spread on the counter-cultural currents of the 1968 uprisings across the globe, the Iron Curtain proved to be as porous as it was in the case of contemporary art's turn towards conceptualism. This article examines East European artists’ approaches to the natural environment and their engagement with green thought against the political, social and environmental background of real existing socialism, in which the party not only attempted to cover up the actual state of environment pollution but also to keep control over access to ecological discourse. Through the dematerialised practices of Slovenian OHO Group, Croatian group TOK, Slovak artist Rudolf Sikora and Czech Petr Štembera, it considers their critical stance towards the communist system's promethean take on nature, awareness of the social and existential aspects of environmental crisis in urban centres, investigation of cosmological dimensions as a strategy to distance themselves from the ideological contamination of the socialist public sphere, interest in phenomenological, non-hierarchical encounters with the natural world, as well as new-age experiments in communal living on the margins of socialist society. By asking how far their understanding of ecological issues was coloured by the socialist system itself and the extent to which their green critique offered an antidote to its limitations, this article proposes that the coalescence of ecology and conceptual art in the wake of 1968 could also be considered a tipping point in the slow-burning crisis of socialism, pointing the way to its subsequent implosion under the strain of social, political and environmental pressures.