The Scottish subsea technology firm will lay 800 metres of cables between the 73 turbines, for which the foundations are now being installed.
Ecosse said it will add an extra 30 staff to its existing 60-strong team to complete the contract.
The Atlantic Carrier support vessel will be used for the work, which is expected to last up to ten months.
Ecosse previously carried out seabed preparation and boulder clearance work on the same project, but this is the company's first renewables cable-lay contract.
The 219MW project is being developed by E.on and will see 73 Vestas V112-3MW turbines installed. It is expected to be commissioned in 2015.