Denton Hall and Eversheds have been appointed as Barclays Bank's advisers on all its property management, purchases and sales.
Barclays has divided its property work into three portfolios of about 2,500 buildings in total.
Denton Hall's two portfolios cover nearly 2,000 properties in the Midlands, the South East and the South West of England.
Eversheds refused to comment on the details of its portfolio, but insiders say it includes 600 properties in the North East.
Barclays previously used about 20 firms in an ad hoc way on its property business.
Addleshaw Booth & Co, Shoosmiths & Harrison and Lovell White Durrant are said to be among the firms that handled the majority of its property work in the past.
A spokesman for Lovells confirms it has not been awarded any of the three Barclays portfolios. But he says that the firm continues to advise the bank on other areas of property law.
He adds: "We are the central service of legal advice on property services, facilities management and capital projects."
Martin Quicke, the commercial property partner leading Denton Hall's team on the portfolios, says: "The managing of 2,000 properties means we will be doing a substantial amount of work for Barclays.
"Barclays organised to appoint only one adviser for each of its three portfolios a couple of years ago, but it has taken them this time to scrutinise the firms involved."
He adds: "They were confident of our abilities to appoint us to two portfolios. The third is going to Eversheds, but it comprises less than a third of the properties. The portfolios were not divided up equally."
Denton Hall plans to do the majority of the work in its Milton Keynes office, but the more specialised areas will be dealt with by its London office.