A method of warming a catalyst of an exhaust gas treatment system of a hybrid vehicle includes transitioning a rotational speed of an engine to within a pre-defined speed range with an electric motor, and reducing an engine manifold pressure to within a pre-defined pressure range. The engine is fueled after the rotational speed of the engine is within the pre-defined speed range, and the engine manifold pressure is within the pre-defined pressure range. While the engine is being fueled, the engine manifold pressure is increased to within a catalyst light-off pressure range, and the torque output of the engine is increased to within a catalyst light-off operating torque range. The exhaust gas produced from the operation of the engine within the pre-defined speed range, within the catalyst light-off pressure range, and within the catalyst light-off operating torque range heats the catalyst while minimizing emissions.