With a background in amateur level cross-country skiing, Oskar came in contact with the sport of triathlon in 2007. He started to compete nationally in 2011 and did his first Continental Cup in 2015. His greatest triathlon achievement so far is becoming National Champion 2016, just five years after he started competing in the sport. Since then he has won several medals in national championships, as well as winning the national series. He has been to many countries competing at Continental Cup and World Cup level. He was also 9th at the European Championships in Middle Distance 2018.