Slade was appointed manager of Leyton Orient on 5 April 2010, six matches before the end of the season. The club was in danger of being relegated from League One, but Slade revived the club's fortunes, helping Leyton Orient to take 10 points from their last six matches, resulting in them avoiding relegation by a single point. Slade was rewarded with a new two-year contract on 14 May and the following season he guided Orient to seventh place, one point outside the play-off places, as well as a fifth round replay at Arsenal in the FA Cup. During the season, Orient chairman Barry Hearn rejected an approach from Barnsley for Slade. Leyton Orient were unable to match their previous year during the 2011–12 season and the club finished in 20th, but the next season Slade was able to guide them to another 7th-place finish.