It was in 1974 that the successor to the popular O302 series, the O303 was launched. Though visually similar to the earlier model, the design lines of this new bus were comparatively smoother. 

This new model had powerful V6 and V8 diesel engines, air-suspension, automatic suspension, single windscreen (in few models) and a wide option with various seating configuration of  9, 10, 11, 13, 14 and 15 rows of seats. This bus model was so ideal for inter-city travel that were produced for nearly 2 decades until the 1980s.

This model had 15 passenger seats and so was called Mercedes-Benz O303-15.