At the 1928 Amsterdam Olympics, Osiier competed in five fencing events (every event Denmark entered). In the individual sabre competition, he reached the semifinals. In individual foil, he won his elimination pool, but was again eliminated in the semifinals after finishing 5th in his pool. Denmark was eliminated in the quarterfinals in team foil, but not because of Osiier, who won 16 of 20 bouts in the competition. In épée he got no further than the semifinals. Denmark was eliminated in the first round of the team épée, although Osiier won five of his eight bouts.