Transport for London said more than 13,000 land and property interests will need to be acquired before construction of the £15.9 billion railway starts in 2010. The panel comprises Ashurst, Cripps Harries Hall, Eversheds and Wragge & Co.
"Such is the scale of Crossrail and its critical importance to London's transport network that a considerable amount of property and land must be acquired in a short space of time," said legal services director Mark Fell.
"Only with all that in place can construction begin and therefore this legal panel will provide invaluable support to the in-house legal teams for Crossrail and Transport for London during this key phase," he added.
Crossrail will run 118km from Maidenhead and Heathrow in the west to Shenfield and Abbey Wood in the east. It is due to open in 2017.