The OA vz. 27's armored body was mounted on a purpose-built ladder frame chassis. The chassis design was unusual as it could be driven in both directions as it had both forward and rear drivers. Both axles could be driven and steered, but not at the same time as the reverser lever controlled the direction of travel and which axle was being used so it was not a true four-wheel drive design. . The forward driver sat on the right side using an observation port protected by an armored shutter with a vision slit. The assistant driver sat on the left and had his own vision port. The rear driver sat on the vehicle's left side. A heavy Schwarzlose MG vz. 07/24 water-cooled machine gun was mounted in the center of the rear hull with 72° of traverse. The crew accessed the fighting compartment from doors in both sides of the vehicle and a hatch in the turret. The gunner sat in a small, conical turret with 360° of traverse. It had an observation port in the front, vision slits on both sides and an armored searchlight on a swing arm in the rear. The turret had a Schwarzlose MG vz. 07/24 machine gun in a forward-facing ball mount and two other ball mounts were fitted on the sides of the turret. A ZB vz. 26 light machine gun was carried inside the vehicle. 5750 rounds were stored for the machine guns. The body had an internal frame of steel "angle iron" beams to which 5.5 mm (0.22 in) armor plates were riveted.
The 5.7 litres (350 cu in), water-cooled, 60 horsepower (45 kW), 4-cylinder Škoda gasoline engine was mounted in the front of the vehicle. It gave a top speed of 35 kilometres per hour (22 mph). It could cross a ditch .4 metres (1.3 ft) wide, climb an obstacle .2 metres (0.66 ft) high and ford a stream .3 metres (0.98 ft) deep.
The OA vz. 27 was the third in a line of Škoda armored cars that used the same revolutionary chassis design. The PA-I introduced the two driver concept, but it had four-wheel drive and four-wheel steering and a turret with two machine guns. Only two prototypes were built before the army asked for further improvements. The PA-II kept the same chassis, but dropped the turret in a completely new body design with curved plates that mounted a machine gun in each corner of the vehicle. The curved armor was very good ballistically, but was quite expensive to manufacture. Twelve were ordered, but the cramped fighting compartment and lack of space for both gunners to man their weapons simultaneously meant that the army was still not satisfied.
The PA-III was intended to be smaller, more mobile and less expensive than its predecessors. Flat armor plates replaced the curved armor of the PA-II and a turret was reintroduced. One prototype was bought in 1925 with an iron body and evaluated for two years before it was accepted in July 1927. Twelve chassis had already been delivered in 1925 while the Army tried to decide the best layout of the body, but it took almost another two years before the last OA vz. 27, as the Army designated the P-III, was delivered in October 1929.