Peak oil has acquired prominence in the political lexicon of an increasing number of critical and radical perspectives during the ongoing ecological and economic crisis. By examining examples within academia as well as initiatives such as the Degrowth Movement and the Transition Network, this paper documents how a series of red-green discourses and movements mobilise the narrative of peak oil as an alarm bell that signals the inevitability of the present ecological crises and of the coming collapse of the fossil-fuel economy. The paper, developing an analysis on two levels, argues that the ‘red-green’ mobilisation of peak oil is problematic. First, a close reading of red-green discourses shows how the weaknesses of the narrative highlighted in the literature (such as a naturalising and de-politicising understanding of the materiality and finitude of oil) are reproduced by the red-greens. Second, building on discourse and political theory, the paper highlights that red-green interpellations of peak oil fail to transcend hegemonic discursive structurations in the field of environmental and energy security, where geopolitical apocalyptic imaginaries and biopolitical forms of securitisation are linked in reproducing post-politicisation processes. Hence, the paper insists that the invocation of peak oil forecloses the possibilities for radical alternatives to the present socio-ecological regime of accumulation and circulation.