In summer 2017 he took part in three competitions as part of the Nordic Combined Grand Prix . The best results were two 30th places, which made him 65th overall. On January 20, 2018, he achieved his first podium finish in the Continental Cup in Rena as third. At the Nordic Junior World Ski Championships in 2018 he won the bronze medal together with Simen Kvarstad , Andreas Skoglund and Einar Lurås Oftebro. On March 10, 2018, he competed in Oslo for the first time as part of the World Cup and was able to score his first four World Cup points straight away. In the overall World Cup ranking he finished 63rd and in the Continental Cup he reached 28th place.
On the first World Cup weekend 2018/19 in Lillehammer , he initially missed the points twice before he was able to win four points again on the third day of competition. Nevertheless, Oftebro was downgraded to the Continental Cup again, where he drew attention again with two wins in Klingenthal . After he reached seventeenth place in the World Cup in Val di Fiemme in mid-January , Oftebro went to the Nordic Junior World Ski Championships 2019 in Lahti, Finland, as a favorite . In fact, he won the bronze medal in the sprint behind Julian Schmid and Johannes Lamparter , whereas in the individual competition on the normal hill and over ten kilometers he missed the medal ranks in sixth. Together with Aleksander Skoglund , Kasper Moen Flatla and Andreas Skoglund, he also finished second in the relay. In early March, Oftebro achieved his best result to date, when he finished sixth in the World Cup in Oslo . He finished 40th in the overall World Cup ranking.
After Oftebro initially did not take part in the Grand Prix in summer 2019, he was finally nominated for the last two competitions in Planica . There he showed himself in a strong early form and reached the podium in third place in the second competition. At the beginning of winter he was runner-up in the Gundersen singles at the Norwegian Championships . A few days later he was able to produce strong performances at the World Cup opener in Ruka , where he took third place in all three competitions and thus established himself among the world's best. He was then named FIS Athlete of the Week. In the further course of the season, Oftebro consistently achieved top results. He also delivered convincing performances in Oberstdorf at the end of January 2020. First he won the relay competition together with Espen Bjørnstad , Jørgen Graabak and Jarl Magnus Riiber , before the next day he achieved his best career result in second place. Oftebro started as a top favorite at the Nordic Junior World Ski Championships 2020 in Oberwiesenthal at the beginning of March 2020 , where he lived up to expectations. As the leader, he went onto the cross-country ski run with a lead of 52 seconds , on which he gave his competitors no chance and was junior world champion ahead of last year's winner Johannes Lamparter and Gaël Blondeau .
Others
His brother Einar is also a Nordic combined athlete. Together with him he received a talent scholarship from SpareBank 1 Østlandet in September 2019.