Osborne has reported a 46 per cent drop in pre-tax profit in its latest financial results.
Pre-tax profit fell to £3m for the year to 31 March 2016, down from £5.6m the year before.
The group said improved margins in its infrastructure and property services businesses were offset by the final settlement of “a small number” of legacy projects won during the recession.
Despite this, the firm saw turnover grow by 11 per cent to reach £342.2m, up from £308.9m a year earlier.
The largest share of the group’s turnover came from education work, with the sector accounting for £107.5m of turnover, up from £78.9m a year earlier.
This is in contrast to the group’s 2015 results, where rail work contributed the largest proportion of turnover at £90m.
Rail (£88.3m) and highways work (£32.6m) still accounted for more than a third of the group’s turnover in 2016, while housing new-build and maintenance contributed a combined £70.1m.
The group’s 12-month order book as of April 2016 was up by 9 per cent year on year to stand at £264m, compared with £242m a year earlier.
Osborne also has £55m of work at second-stage or single-source negotiation, while its total secured order book now stands at £639m, up from £534m a year earlier.
The firm said frameworks with Highways England and Network Rail have both made significant contributions to its order book during its most recent financial year.
According to official figures, Network Rail spent £84.7m with Osborne in the 12 months to March 2016, or 1.2 per cent of its total supplier spend.
Osborne has appointed three new board members in the past two months, with Stuart Hammond and former CBRE chairman Michael Strong joining the business in September, while Osborne Property Services MD Nick Sterling was promoted to the board earlier this month.