A Prince George's County special grand jury indicted seven men yesterday on sexual assault charges of forcing, or trying to force, other men to have sex with them in the County Detention Center in Upper Marlboro.

The special grand jury was impaneled in September after a Washington Post series in which inmates described a dozen rapes and sexual assaults in the county jail. Inmates and guards said in the series that about a dozen sexual attacks occurred a week at the jail.

Four of the men indicted yesterday were quoted in the series as saying that they participated in sexual assaults in the jail. The other three were mentioned in a December follow-up article on recent sexual assaults in the jail.

Among those indicted were William Henry Daniels, 21, and Perry Scharod Edon, 30, in an incident Jan. 8, 1982, in which Daniels and Edon allegedly forced a restaurant cook named Tyrone Blair, 26, to perform oral sex in the jail. Blair was awaiting trial at the time on a charge of malicious destruction of property for breaking his brother-in-law's living room window. Daniels was awaiting trial on charges of first-degree murder and armed robbery and Edon was serving a 90-day sentence for failure to provide child support.

In the Post series, Edon said that he forced Blair to perform oral sex because he was afraid that Daniels would rape him if he did not go along with Daniels. Daniels told of hitting Blair in the face and having oral sex with him.

Edon is currently employed by a printing company and Daniels, who was convicted on both of his original charges, is serving a life-plus-eight-year sentence at the Maryland Penitentiary in Baltimore.

They were indicted yesterday on two counts of second-degree sex offense, assault and battery, false imprisonment, and assault with intent to commit a second-degree sex offense. A second-degree sex offense is a sexual assault by one attacker. A first-degree offense occurs when one or more persons help another person assault someone sexually.

Also indicted yesterday were Wallace (Bam Bam) Parker Jr., 28, and Clifton Earl Tucker, 19, in a Feb. 14, 1981, assault against a Forestville house painter. The painter was raped anally, according to the indictment and jail medical records. At the time, Parker had been convicted of armed robbery and was awaiting transfer to the Maryland Penitentiary; Tucker was awaiting trial on an armed robbery charge, and the painter was awaiting trial on a burglary charge.

The February incident was not mentioned in the series, although both Parker and Tucker were quoted in the series as admitting to separate incidents of sexual assault against other men in the jail.

Parker and Tucker were indicted on charges of second-degree sex offense, assault and battery, false imprisonment, and assault with intent to commit both a first degree and second degree sex offense.

Both Parker and Tucker are now serving sentences for armed robbery. Parker is in the Maryland Penitentiary in Baltimore and Tucker is in the Maryland Correctional Institution at Hagerstown. The painter, who was convicted of his charge, is serving a sentence at the Maryland Correctional Training Center.

Robert Patrick Garnett, 24; Kirk Williams, 27, and Anthony Majette, 22, were each indicted yesterday on two attempted first-degree sex offenses for anal sex and oral sex against James Allen Anderson Jr., a Pennsylvania janitor who is in the county jail awaiting trial on a murder charge. Anderson was sexually assaulted in November in the jail, he said in a December story in the Post.

His accused attackers were also charged with assault with intent to commit a first-degree sex offense, assault with intent to commit a second-degree sex offense, assault and battery, and false imprisonment for a Nov. 27 incident at the jail.

Anderson told a reporter that Garnett, of Northeast Washington, and Williams, of Beltsville, beat him and stuck pencils into his rectum.

Anderson said Majette, of Southeast Washington, was a witness. The attack was confirmed by Dr. Dennis Frank of Prince George's General Hospital, who found "trauma" to Anderson's anus and abrasions on his scalp, according to medical records.

During separate interviews, Garnett and Williams denied assaulting Anderson. Williams said he was not even in the cellblock at the time of the alleged attack, but Majette said he saw Williams "bodypunching" Anderson in the cell. Majette said, however, that Garnett was not in the cell at the time.

After the series was published, reporter Loretta Tofani was subpoened to appear before the grand jury. Lawyers for Tofani fought the subpoena, saying that her investigation for the newspaper was continuing and that her ability to continue to interview inmates and officials would be impaired if she were to testify.

Tofani's lawyers argued before Circuit Judge Arthur M. Ahalt that the series already had provided the information that prompted the grand jury investigation. But Ahalt ruled last month that Tofani must testify.

Earlier this week, however, the judge agreed to excuse her while the subpeona is appealed by Tofani to the Maryland Court of Special Appeals.

Robert C. Bonsib, the assistant state's attorney in charge of the grand jury prodeedings, would not comment on what effect yesterday's indictments would have on the subpoena of Tofani, except to say the investigation is continuing.