Ossa entered the competition with its debut at the 1952 ISDT in Austria.
In 1957, the 125A was replaced by the 125B with a pressed steel frame, hydraulic suspension at the front and rear, and a more powerful engine. This was followed by the 125C with a tubular frame. The following year saw the launch of the company's only four-stroke model, the 175GT with a Morini engine.
Ossa had gained a new star in 1954 with the hiring of Sandro Colombo, who was known for his previous work at Gilera. Colombo had developed an engine for Ossa that was constantly evolving and became the main focus for the company's new models. The engines were installed in the 160T and GT, and the displacement was increased to 175, 230, and 250 cm³ for a series of new models. The 250 engine powered the machine that won the 1967 24-hour race at Montjuïc. A series of impressive competition results followed.
Off-road models were developed and Mick Andrews joined Ossa in 1967. Riding his Ossa Plonker, he dominated the trial championships in the early 1970s and won the European Trial Championship in 1971 and 1972. Ossa released a machine in his honor, the Ossa MAR - the Mick Andrews Replica, which was produced until the late 1970s. Andrews also won the Scottish Six Days Trial three years in a row - in 1970, 1971, and 1972. Ossa was also very successful in the United States, where a model called the Ossa DMR—the Dick Mann Replica—was released. An interesting machine from this period is the Yankee 500, an American motorcycle powered by a newly developed Ossa twin-cylinder engine for road racing.
The Ossa motocross series of the 1970s was very well received, and the Phantom models of the 70s regularly appeared in the results of all levels of competition in Europe and the United States.
