The legislation, which won overwhelming approval in the State Senate and Assembly last month, sets the boundaries for the college's Broad Hollow Bioscience Park at 38.5 acres.
It also paves the way for construction of a third building at the park.
The new structure would house start-up companies while OSI would expand into an existing second building.
OSI makes the lung cancer drug Tarceva.
Cuomo's action comes after OSI, under a previous owner, announced plans to leave Long Island for Westchester County, in part because of state construction and procurement laws that it said hindered expansion on a SUNY campus.
The new law exempts incubator tenants from the regulations.
OSI's new owner has committed to keeping research and development operations at the college, adding 135 jobs to its workforce of 90 there. However, its Melville headquarters is being phased out, with the loss of 150 jobs.
Sweeney said yesterday, "This new law brings us one step closer to making Long Island a leader in the biotechnology industry."
Fuschillo agreed, predicting the park expansion would "create hundreds of jobs and tens of millions of dollars in new revenue" for the region.