The approvals came despite proponents being significantly outspent by opponents, according to a May 21 article in the Portland "Oregonian" newspaper.
In Jackson County, voters passed the measure 119-15. Proponents raised $375,000 compared with nearly $1 million by opponents, which included Monsanto, Syngenta and DuPont Pioneer.
The Finland, Minn.-based Organic Consumers Fund donated $50,000 to Oregon campaigns. The Washington, D.C.-based Center for Food Safety also contributed to the efforts.
In Josephine County, the measure passed 58-17.
The Josephine County measure also will be tested in court since its passage came after an Oregon law was enacted in October 2013 that prohibits counties from passing bans on GMOs, or genetically modified organisms.
The Jackson County measure is exempt because it had qualified for the ballot before the state Legislature passed Senate Bill 863.
Proponents say passage of these two measures bodes well for Ballot Initiative #44, which will go before state voters in November. That measure would require labeling of all foods that are made from or contain GMOs.
This is not the first time that county voters have approved a measure to ban growing of GMO crops. Others include Santa Cruz, Trinity, Marin and Mendocino, all in California; and San Juan County, Wash.
Vermont has passed a law banning GMO crops, set to take effect 2016, but it is likely to face legal challenges in court.