A self-propelled low-emission off-road vehicle has an internal combustion engine supported in an engine compartment and also includes a vehicle cooling assembly and an engine exhaust treatment device positioned in the compartment. The vehicle cooling assembly includes a powered fan and an enclosure with a heat exchanger operable to discharge heat produced by the vehicle. The enclosure presents an inlet, outlet, and air flow plenum, with the fan directing air flow along a path between the inlet and outlet. The exhaust treatment device is operable to treat engine exhaust flow. The exhaust treatment device is positioned at least partly in the air flow plenum and in the path between the inlet and outlet.