CAMBRIDGE, Mass.--A Harvard professor and his wife, a church administrator, were indicted yesterday on charges of sexually assaulting their grandchildren, authorities said.

Andrew W. Mellon Professor on the Humanities William L. Moran, 64, a specialist on ancient Assyria, and Suzanne D. Moran, 61, administrator of the First Congregational Church in Cambridge, were charged with sexually assaulting their grandchildren from June 1985 to June 1987, said Thomas Samoluk, spokes-person for Middlesex County District Attorney Scott Harshbarger.

Mrs. Moran is charged with forcible rape of a child under the age of 16 and indecent assault and battery on a child under 14 on various dates. Samoluk said part of the charge involved the use of a sharp instrument and threats made to the children that their parents would be killed if they spoke of the abuse.

Professor Moran is charged with rape and abuse of a child under 16 and indecent assault and battery of a child under 14.

Telephone calls to the congregational church went unanswered yesterday.

Mrs. Moran referred calls to her attorney, Brackett Denniston, who said his clients are innocent of the charges. "They expect to plead innocent. They are innocent and expect to be vindicated after vigorously contesting the charges," Denniston said.

Arraigned Today

Margery Heffron, a Harvard spokesperson, confirmed that Moran was a professor. She declined further comment.

The Morans were scheduled to appear at an arraignment today before Judge Hiller Zobel in Middlesex Superior Court.

Samoluk said the Massachusetts State Department of Social Services and the district attorneys office were contacted about the case in November after the victims' parents had moved to another state and noticed abnormal behavior in the children.