The aircraft, an ATR 42-300, was landing at Donegal Airport (EIDL) in strong winds following a scheduled passenger flight from Dublin Airport (EIDW). During the landing roll, after the aircraft had touched down on the runway, it veered to the left and departed the tarmac surface onto the grass adjacent to the runway. The pilot steered the aircraft back onto the runway and came to a halt. Following a brief discussion between the crew, it was decided to continue to taxi the aircraft to the parking stand. The passengers disembarked normally. There were no injuries reported to the Investigation and the aircraft was undamaged. Probable Cause: Runway excursion during the aircraft?s landing roll due to a strong gusting crosswind. Contributory Cause: 1. A narrow runway of 30 m in width. 2. The susceptibility of high-wing aircraft to control difficulties during the landing roll in crosswind conditions.