The EDAW consortium and multidisciplinary consultants Arup and Atkins have been chosen to design the Olympic park and infrastructure.
The appointment, which was predicted in Building on 13 January, was confirmed on Tuesday.
Higgins said: "I am delighted to announce this appointment.
Getting the site infrastructure and landscape right is a key task for the ODA over the next two years."
The EDAW team, led by director Jason Prior, will now amend and extend the bid-winning masterplan and design the infrastructure elements of the park.
The design for the Olympic venues and athletes' village will be tendered separately.
London mayor Ken Livingstone praised the appointment. He said: "This appointment is critical in helping us shape the long-term legacy of the London Games."