This invention is directed to a process for increasing production of product that is formed in a reactor having a combustion section in which fuel is burned to produce heat to drive an endothermic reaction occurring within a reaction section. Production is increased by adding supplemental oxygen to air or other oxygen containing gas used to support combustion in the combustion section, thereby to generate more heat to support an increase in the endothermic reaction. Additionally, supplemental oxygen can be introduced into the reaction section to partially oxidize a reactant to generate heat and to allow an increase in the production of the product. Supplemental oxygen may be added directly to the steam-methane mixture, or to the combustion air.