The plant has been in operation for more than 50 years. The company was founded in Brooklyn in 1898 by William Entenmann, who moved to a small store in Bay Shore in 1905. The company relocated to the current facility in 1961.
Entenmann's parent company Bimbo Bakeries USA says it is shifting production to other plants that are more efficient.
Most of the 265 workers in Bay Shore will lose their jobs. At its peak, the plant employed 1,500.
The facility will continue some operations, like sales and distribution.
Bimbo Bakeries USA is the U.S. arm of Mexico's Grupo Bimbo.