Despite remaining with McLaren, rumours persisted that Newey wanted to leave the team, and by late 2004 his future began to look uncertain when speculation began that the engineer could return to Williams or even leave the sport completely. Despite strenuous denials from Ron Dennis stories continued to circulate during the 2004/2005 off-season that Newey's departure was imminent. In April 2005, it was confirmed that his contract with the team had been extended by six months to the end of the year at which point he was expected to take a sabbatical or retire from Formula One design completely, but on 19 July instead he stated that "this step can wait" and he would remain with McLaren for the year 2006.
Despite those assurances, Red Bull Racing announced on 8 November 2005 that Newey would join the team from February 2006. The Guardian reported that Newey would be getting around $10 million a year at Red Bull Racing, owned by Austrian energy drink billionaire Dietrich Mateschitz, after McLaren baulked at increasing his salary in contract renewal negotiations.
Newey could hardly influence the design of the 2006 car and Red Bull's season started with poor results, having scored only two points from six races. However, the team's lead driver, David Coulthard, who had driven Newey-designed cars for years for both Williams and McLaren, managed to secure third place and six points in the Monaco Grand Prix. Although assisted by retirements of other competitors, indications were that the team was eventually beginning to pick up where it left off in 2005 when they finished a close seventh overall. The 2007 Red Bull of his design was powered by the Renault RS26 engine as the Ferrari 056 contract was transferred to Scuderia Toro Rosso, Red Bull Racing's "B team". The car was reasonably fast but rather unreliable, with each driver retiring seven times in a season of 17 races. Nevertheless, with the disqualification of McLaren-Mercedes, Red Bull achieved fifth place in the 2007 Constructors' Championship as targeted. Technical directors Adrian Newey and Geoff Willis noted that the 2008 chassis was the most intricate design to have rolled out of their factory. The season started well for the team, with Mark Webber scoring five consecutive points finishes and Coulthard claiming a podium at Montreal. At the half-way mark, Red Bull was in a fierce battle for fourth place in the Constructors Championship, along with Renault and Toyota. However, Red Bull scored just five points in the second half of the season (compared to 24 in the first half) as the team slipped down the grid. Even Toro Rosso managed to outscore them by the end of the season.