We report the exploitation of thermal effects and bifurcation (ignition and extinction) behavior to enable steady-state operation of an Oxidative Coupling of Methane (OCM) reactor with ambient feed and furnace temperature. Using a simplified kinetic and reactor model and results from bifurcation theory, we explain the experimentally observed ignition-extinction behavior for catalysts of different activity and reactor tubes of varying diameter when the furnace temperature or the space time are varied. We apply the theory to analyze the impact of reactor tube diameter and heat loss on the feasible region of autothermal operation and present experimental evidence for the existence of isolated high temperature/conversion branches. The results indicate that when catalyst activity is high enough, it is possible to operate an OCM reactor autothermally using the reactor feed (at ambient temperature or lower) as coolant, which enables the maximum practical single-pass methane conversion. (C) 2017 Elsevier B.V. All rights reserved.