Bishop said he would consider publishing a list of DfL's preferred contractors following a practice similar to that used by councils.
He insisted that he does not want the agency to be regarded as "some sort of shadowy organisation that exerts an influence from behind the scenes".
The assembly's planning and spatial development committee said the move would make DfL's processes more transparent and protect it against accusations of favouritism.
Chairman Tony Arbour explained: "It is imperative that DfL is open and transparent in procuring the best architectural talent."
Arbour also asked whether DfL would insist on a certain design style on major projects such as Crossrail. In reply, Bishop said the Jubilee Line is a good model for Crossrail because it has a consistent style but different designs at each station.
