A husband and wife were arrested and charged yesterday with stealing more than 11 tons of butter over more than two years from the Maryland and Virginia Milk Producers Association plant in Laurel.

Maryland state police said they think considerably more butter may have been stolen from the plant and are continuing to investigate. They said further arrests are possible.

Michael A. Kidwell, 24, and his wife, Barbara Ellen Kidwell, 23, were accused of stealing 622 36-pound cases, or 22,320 pounds, of Land O' Lakes butter from the plant and selling it to restaurants and individuals in the Greenbelt and Hyattsville areas at prices far below wholesale price. The Kidwells were allegedly selling the butter for $50 a case. The normal retail price was at least $68 a case.

Kidwell, of 13304 Deerfield Rd., Laurel, was employed at the dairy plant when the thefts allegedly occurred from the fall of 1979 until this spring.

Police said butter was stolen only in the late fall, winter and early spring because the thieves lacked adequate refrigeration to keep it in warm weather.

Buyers of the stolen butter are not subject to arrest, police said, because they were under the impression they were purchasing it from the plant at a special discount.

Police said the dairy didn't miss the butter until several customers asked for the reduced price. State Police said Prince George's County police became suspicious that butter was being stolen in January when a car stopped for a traffic violation was found to contain 72 pounds of butter. The driver turned out to be a purchaser of the butter.

A month ago, the dairy hired a private investigative firm, Sting Security, to make an undercover investigation. Sting Security turned its findings over to the state police a week ago.

If convicted of theft and conspiracy of theft, the Kidwells could be sentenced to as long as 15 years in prison and fined $1,000.