[9] In late 2018, he was included into the provisional entry list for the 2019 Moto3 season with the Red Bull KTM Ajo team, despite being younger than the usual minimum age requirement of 16.

[16] For 2018, as well as competing in the Rookies Cup, both Can and Deniz joined Ajo Motorsport[17] and also raced in the FIM CEV Moto3 Junior World Championship.

Öncü benefited from a 2018 change to the FIM regulations,[18] that added the current Red Bull Rookies Cup Champion to an exemption already given to the FIM Junior World Championship winner allowing them to compete in Moto3, a series normally requiring an adult licence, at a minimum age of 15 years rather than the usual 16 years.

Despite his early promise shown as Red Bull Rookies champion and winning on his debut wildcard entry, Öncü struggled in the class, scoring only three points finishes from 16 contested races and finishing with 8 points in 31st position of the riders' championship.

He continued with the team for 2021, finishing regularly in the top 10 and taking his first podium at the French round.