A method and apparatus for low NO.sub.x combustion in natural draft combustion chambers comprising staged-air combustion apparatus and process in which a fuel-rich, fuel/air mixture is introduced through a burner into a combustion chamber, forming a fuel-rich primary combustion zone flame. The fuel-rich primary combustion zone flame is attached to a flame guide disposed substantially parallel to the longitudinal axis of the primary combustion zone flame and extending from behind the burner. The flame guide also provides for removal of heat from the primary combustion zone flame. Secondary combustion air is introduced into the combustion chamber downstream of the burner to complete combustion of the fuel-rich primary combustion zone flame products. Internal recirculation of combustion gases within the combustion chamber into the fuel-rich primary combustion zone flame stabilize the fuel-rich primary combustion zone flame and contribute to emissions reduction.