The contract calls for delivery of 141 Marine versions of the helicopter and 26 Air Force versions by October 2014.
The V-22 Osprey takes off and lands like a helicopter but flies like an airplane. Some have been deployed to Iraq.
"The V-22 Osprey is a cutting-edge aircraft that has already proven its tremendous worth on the field of battle," said Sen. John Cornyn, R-Texas.
There have been concerns about its reliability over the years, but it continues to win financial support in Congress.
Bell Helicopter is a division of Textron Inc. The V-22 is a joint venture of Bell and The Boeing Co. It should replace aging, Vietnam-era CH-46E helicopters.