In November 2007, Onidi took part in the four race Italian Formula Renault 2.0 Winter Series with RP Motorsport, taking two podiums to finish third in the standings.

[3] In the accompanying Italian Formula 3000 series, he also ended the year as runner–up, finishing a single point behind Durango's Colombian driver Omar Leal.

[4] Onidi remained in the championship in 2009, moving to fellow Italian team Fisichella Motor Sport to partner Rodolfo González.

[5] He again took two victories during the season, at Portimão and Vallelunga, but despite leading the championship heading into the final round at Monza, he finished third in the standings, behind Marco Bonanomi and eventual champion Will Bratt.

[8] He remained with Lazarus for the 2011 and was joined by compatriot Fabrizio Crestani; the two proved evenly matched, finishing fifth and sixth in the championship with Onidi seven points ahead.

Onidi made his A1 Grand Prix debut in October 2008, racing for A1 Team Italy at the first round of the 2008–09 season at Zandvoort in the Netherlands.