Tost's racing career began at an early age when he competed in Formula Ford and Formula Three, before working as a team manager at the Austrian based Walter Lechner Racing School. In 1993, he joined Willi Weber Management, best known for managing Michael Schumacher, where he looked after Ralf Schumacher's early career in Japan.

His first foray into F1 was in 2001 when he moved to BMW, where he worked as track operations manager until he moved to the newly-formed Toro Rosso (previously Minardi) in 2006. The team finished their first season with a single point, but they finished the following year with eight points, meriting a respectable sixth place.

However, the season was not without controversy, as American Scott Speed was dismissed in July 2007 after his third successive retirement. After spinning out in heavy rain at the Nürburgring, the American was reportedly involved in a physical altercation with Tost, which the Toro Rosso boss denied. Speed subsequently launched a verbal attack on him, claiming he was "out of control".

At the end of the 2007 season he was accused by David Coulthard of circulating rumours of a move to Red Bull for two-time world champion Fernando Alonso. Coulthard, who had already signed a contract with Red Bull for the 2008 season, claimed it was inappropriate of him to comment on the team owned by the same parent company.

His greatest moment in the sport came at the 2008 Italian Grand Prix when Red Bull protégé Sebastian Vettel qualified on pole and went on to take a lights to flag victory. However, the other teams were not as impressed and demanded that Toro Rosso constructed its own chassis rather than using a Red Bull. The FIA agreed and from 2010 onwards Toro Rosso have been on their own.

Never a stranger to controversy, Tost changed his driver line-up mid-season again in 2009. After a string of disappointing results, Toro Rosso released veteran ChampCar driver Sebastien Bourdais and replaced him with 19-year-old Jaime Alguersuari, who became the youngest driver in the history of F1. Bourdais threatened legal proceedings for unfair dismissal, and he also alleged he was sacked via text message, but this was strenuously denied by Tost.

His decision to introduce Alguersuari - the Spaniard never having driven a single lap in an F1 car - sparked further outrage, with drivers claiming Alguersuari threatened the safety of other competitors. In 2010 he kept Alguersuari and Buemi but the car was nothing special and the team lacked the resources to develop it.

2011 brought more success and 41 points, meaning Toro Rosso finished comfortably ahead of Williams in the constructors' championship. However, Alguersuari's and Buemi's opportunity to impress had run its course and both were dropped in favour of the next generation of Red Bull proteges, Daniel Ricciardo and Jean-Eric Vergne.