Bieler, who competes for the Gardes Frontiere , took part in U20 races in the cross-country Alpine Cup from 2011 to 2013 . He finished seventh in the 2011/12 season and fifth in the 2012/13 season . At the European Olympic Winter Youth Festival 2011 in Liberec , he achieved 43rd place over 10 km classic, 41st place in sprint and 24th place over 7.5 km freestyle. In the following year he came at the Nordic Junior World Ski Championships in Erzurum on the 20th place over 10 km classic, on the 16th place in the skiathlon and on the ninth place with the relay. Since the 2013/14 season he has mainly participated in competitions in the cross-country Alpine Cup. In February 2015 in Campra he achieved his first top 10 place with the ninth place over 15 km classic. At the U23 World Championships in 2014 in Val di Fiemme , he achieved 46th place over 15 km classic and 38th place in skiathlon.
He made his debut in the cross-country skiing world cup in Davos in December 2014 , finishing 85th in the sprint and 57th place over 15 km classic. At the U23 World Championships in 2015 in Almaty , he took 20th place in the sprint and 17th place in the skiathlon. The following year he came in 22nd place in the sprint and over 15 km classic at the U23 World Championships 2016 in Rasnov . At the Swiss championships in 2016 he won the bronze medal over 15 km classic and the silver medal in the subsequent pursuit. With the season of Gardes Frontier he became Swiss champion. In February 2017 he got his first World Cup points in Pyeongchang with the 14th place in the skiathlon. At the Swiss Championships 2017 in Val Müstair he came third in the pursuit. In February 2019 he became Swiss champion in the pursuit in Engelberg .
Medals at national championships
2016 : Gold with the relay, silver in the pursuit, bronze over 15 km
Switzerland