The proposal comes two months after California voters rejected a similar ballot measure in a nearly $55 million advertising war that pitted food safety advocates against agricultural and biotechnology giants.
Opponents of food labeling argue it will raise food prices and hurt farmers. Supporters contend that consumers should have a choice of whether or not to eat genetically engineered products, even though the federal government and major science groups say such foods are safe to eat. The supporters promised to take their fight to the Northwest after the California ballot measure failed last fall.
An initiative to the Washington Legislature requires at least 241,153 valid signatures of registered state voters to be certified, though the secretary of state's office suggests at least 320,000 as a buffer for any duplicate or invalid signatures.
On Thursday, initiative sponsors delivered 350,000 signatures inside an ambulance with a sign reading "Label GMO Food" on the side.
Initiative 522 would require food and seeds produced entirely or partly through genetic engineering and sold in Washington to be labeled as such, beginning July 1, 2015. Under the measure, raw foods that are not packaged separately would have to be labeled on the retail shelf.
Supporters say consumers benefit from having more information.
"Yes, you can steer clear of certain items, but unless you know that they're there, how do you know to steer clear of them?" asked Chris McManus, the initiative sponsor and owner of a small advertising firm. "Putting a label on the front of that just informs the consumer a little bit more about what they're buying."
The nation's food labeling system is already built around giving consumers information about health and safety, countered Heather Hansen, executive director of Washington Friends of Farms and Forests.
"We think this is really intended to be a scare tactic, to ultimately scare people away from technology," she said. "And it's not providing any meaningful information."
Once the initiative goes to the Legislature, lawmakers have the option to vote on it, take no action and send it to the November ballot, or recommend an alternative measure that will appear on the ballot with it.
About 50 countries require genetically modified foods to be labeled, but the U.S. isn't one of them. Only Alaska has enacted legislation at the state level, requiring the labeling of genetically engineered fish and shellfish products.
A bill in the Washington Legislature to require food labeling failed to pass out of committee, despite support from a coalition of local wheat farmers who said they feared their export markets will be hurt if genetically modified wheat gains federal approval.
Biotechnology giant Monsanto Co. has announced plans to begin testing genetically modified wheat, though the product is likely a decade or more from being offered commercially.