A 29-year-old mother of three was found slain in a laundry room near her Silver Spring town house early yesterday, and a next-door neighbor was charged several hours later with murdering her.

Debra Julia Donaldson, a clerk at the Giant Food headquarters in Landover, apparently had left her home at 2030 Harlequin Terr. to wash clothes in a laundry room at the rear of the five-unit town house complex Thursday night, according to Montgomery County police spokesman Phil Caswell.

Caswell said Donaldson's children awoke yesterday morning to find her missing and called a friend of hers, who found the woman's unclad body face down inside the laundry room at 7:45 a.m. She apparently had died from throat lacerations, according to police.

Police said there were signs of a struggle and evidence that Donaldson had been sexually assaulted.

About 12:30 p.m., John Cobey, 24, of 2032 Harlequin Terr. was arrested and charged with murder.

According to records in the county prosecutor's office, Cobey pleaded guilty to robbery and assault with intent to rape in February 1977 and was sentenced to concurrent 10-year terms. Details of his imprisonment could not be learned yesterday, but he was eligible for parole after two years.

Caswell said Donaldson, whose body was found near a basket of her family's clothing, had probably been killed about 11 p.m. Thursday. He said neighbors in the Snowden Ridge town house development heard screams about that time, but did not investigate.