The JV will widen a ten-mile stretch of the A14 between Swavesey and Milton.
Main construction work is due to start in late 2016 with the new bypass and widened A14 opening to traffic in 2020.
The deal was retendered in June because Highways England was unhappy with the quality of bids it received.
Leo Quinn, Balfour Beatty Group Chief Executive said: “This is a complex project and our joint venture brings proven expertise and experience in working as part of an integrated delivery model – something which is going to be crucial for the successful delivery of this project.
“The improvements the scheme will deliver will help to relieve congestion on one of the busiest parts of the strategic road network between the Midlands and East Anglia and support national and regional economic growth.”
The wider Cambridge to Huntingdon improvement scheme is subject to statutory approval.
It will be delivered through an integrated delivery team comprising of a number of contractor joint ventures, designers and Highways England employees.
A Costain/Skanska joint venture was chosen in June to deliver two of three sections on the scheme.
Costain/Skanska picked up package 1, covering the A1 junction at Alconbury to the East Coast Mainline and package 2 covering east of the East Coast Mainline to Swavesey.
These two sections alone are worth £600m.
A £35.5m detailed design contract has been also been secured by an Atkins CH2M joint venture.
The fourth main construction package to demolish the viaduct over the East Coast Mainline at Huntingdon and associated works will be tendered in 2019.
The project is the first to be awarded under Highways England’s Construction Delivery Framework.
Stretching over 25 miles, the works will improve this highly congested stretch of road.
The scheme will involve a new major bypass between Swavesey and Brampton, widening the A1 between Brampton and Alconbury, widening the existing A14 between Swavesey and Milton, improving the junctions at Bar Hill, Swavesey, Girton, Histon and Milton, Huntingdon Town Centre improvements, to include the demolition of the viaduct, and a new local access road.
Chris Taylor, Director for Complex Infrastructure at Highways England, leading the A14 Cambridge to Huntingdon improvement scheme, said: “This award is another step closer to our commitment to deliver the A14 Cambridge to Huntingdon improvement scheme.
“Now all three joint-venture contractors are on-board, they will work collaboratively to finalise the pre-construction planning, to deliver the excellence that our customers and stakeholders expect of us.
“While we appreciate our planning application is yet to be fully examined by the Planning Inspectorate and we are yet to receive permission to start construction, this third appointment will add to the support we need to prepare for works getting underway on time and to budget.”