Back in League One, Osborne began the 2009–10 season out of favour and made sporadic appearances from the bench as cover in central defence and full back. He spurned opportunities to move away on loan and finally broke into the starting lineup in March 2010. After being challenged by manager Andy Scott to hold onto his starting spot, Osborne started in 11 of Brentford's 13 remaining matches of the season and signed a new two-year contract in May 2010. Osborne fully established himself in the team and made a career-high 51 appearances during the 2010–11 season, which featured a run to the 2011 Football League Trophy Final.