Osborne will handle responsive repairs, voids management and planned maintenance starting on April 1 2012.
The seven-year deal has the option to be extended by a further eight years and reach more than £225 million in value.
Madeleine Forster, Chief Executive of Ascham Homes, said: “Osborne was appointed through a very rigorous selection process, in which residents played a key role in the specification of the new service and interviewing the contractors.”
Nick Sterling, Managing Director of Osborne’s property services team, said: “This award followed a rigorous test of all bidders’ credentials and we are looking forward to working with Ascham Homes’ enthusiastic team to deliver a service its residents can be proud of.”