Oscar E. Kendall, whose long masquerade as fashion photographer Richard Avedon ended with his arrest in a Washington singles bar in September, was sentenced in D.C. Superior Court yesterday to serve a minimum of seven years and three months in prison for assault with intent to commit rape.

Kendall, 34, who police described as a sophisticated con man, was for years the focus of complaints to police from women across the U.S. and in Canada. They said the tall, baldish man used the glamour attached to the Avedon name to swindle them out of their money and, in some cases, sexually assault them.

As part of an unusual agreement arranged by the U.S. attorney's office here, Kendall pleaded guilty last month to the assault charge and agreed to plead guilty to three theft charges in other cities. In exchange, prosecutors throughout the country and in Canada agreed to drop two rape, 10 grand larceny and five attempted fraud charges.

Before sentencing yesterday on the assault charge by Judge H. Carl Moultrie I, Kendall, in a brief and almost inaudible statement, maintained he was innocent.

"Your honor, I've done many things in my life, but rape is not one of them . . . I did not rape this woman," Kendall told Moultrie.

Kendall entered what is known as an "Alford plea" - taken from the name of a Supreme Court case - which means he contends he is innocent but pleads guilty because of the weight of the government's case and the likelihood of his conviction by a jury.

A memorandum filed by the government with Moultrie in connection with the sentencing detailed Kendall's long criminal record, which dates back to a conviction for Passing a bad check in Arizona in 1963.

Assistant U.S. Attorney John P. Hume contended in the memorandum that since 1974 Kendall's "sole means of support was derived by defrauding women, in many instances of their life savings and in some instances raping them."

Hume described Kendall as "totally without remorse" and said Kendell's "contempt for women is evident throughout his criminal history."

Police investigators have said Kendall would frequent shopping malls and bars, meet women, tell them he was Richard Avedon and promise them the rewards of a fashion modeling career.

According to Hume's memorandum, Kendall told a police detective in California that he knew "it is difficult to prosecute a rapist who, by fraud, gains the confidence and companship of a woman . . ."

Hume said Kendall told the detective, "You can always beat rape charges if you don't put marks on (the women)."

In the Washington case, which occurred in 1974, Kendall met a woman in a Northwest bar, took her for coffee and then accompanied her to her hotel room, where she allowed Kendall to use the telephone, according to the government's case.

Kendall then forced the woman to disrobe, raped her, subsequently falling asleep, at which point the women ran for help, according to Hume. When the woman returned to the room, Kendall was gone, Hume has said.

Leroy Nesbitt, Kendall's lawyer, has contended that if the case went to trial, he would argue that the woman consented to the acts.

Yesterday, Nesbitt asked Moultrie to sentence his client to a minimum of two and a maximum of 10 years in prison for the assault charge. Nesbitt noted that during Kendall's long criminal history, no effort has been made to rehabilitate his client. Two years of imprisonment would be "sufficient time for a man of his age to make an assessment of himself," Nesbitt said.

Kendall stood with his head bowed and his hands clasped behind his back, as Moultrie sentenced him to serve a minimum of seven years and three months and a maximum of 22 years in prison. Kendall will be eligible for parole once the minimum term expires. Technically, the assault charge carries a maximum of 15 years in prison, but because he was convicted of the same charge in 1968 in Florida, Kendall was subject to a sentence of up to 22 1/2 years in prison.