"Anything Arthur asks me to do," said Jacqueline Onassis with a smile, "I'd be happy to do."

The arthur in question was Arthur Schlesinger Jr. and the deed was a donation - of Mrs. Onassis' papers, to Radcliffe College's Arthur and Elizabeth Schlesinger Library on the History of Women in America. In honor of that library, John Kenneth Galbraith, William Paley, Barbara Walters as well as Onassis, Schlester and about 100 other guests, gathered last night in the elegant home of New York writer Lally Weymouth.

Onassis, one of the cocktail party's cohosts with Weymouth and Anna Rosenberg Hoffman, reminisced with Radcliffe President Matina Horner about their separate undergraduate days.

For students at her college now, Horner remarked, nomenclature presents a dilemma.Should they call themselves students at Radcliffe or at Harvard? "Theree are good and bad reasons" for using Harvard, she said. "If you're calling yourself a Harvard student in the same way some first generation immigrants changed their names, that's a weak reason."

The guests crowded into the flower-filled living room dominated by a huge Japanese screen and decorated in peach and plum tones to hear an informal address by Galbraith, who had arrived from Europe just hours before the party. Schlesinger chastized him for having deserted the environmental cause by flying back on the Concorde.

Recalling Harvard in the 1930s, when Radcliffe was separate but not equal. he saluted "the enormous transition to treating women as people."

Historians, Galbraith remarked, are influenced in what they study by the availability of material. The Schlesinger Library, with its growing resources, therefore makes inevitable increased future work on the part women have played in shaping the United States, he said.

As recently as the 1950s, he said, he wondered aloud at a Radcliffe Board of Trustees meeting why its was presumed that Radcliffe's intelligent women "would disapear to New Rochelle to rise ultimately to the auxiliary committee of the local library." A woman trustee silenced him at that time, he said, by retorting that there was nothing so important as being a wife and mother.

Schlesinger spoke of his father's consciousness-raising between 1914 - when he watched a women's suffrage march and wrote that he hoped women would get the vote soon "so that people can concentrate on the real problems" - and 1922, when he lamented in a book that history was being told with a male bias.

Fittingly for a party given to aid a library, much of the conversation was about writing. Many of the guests had celebrated William Stron's new novel "Sophie's Choice" the night before and were still talking about it. Rose Styron came, but apologized for her husband, who she said had gone home to sleep.

Onassis, about whom enough words to fill a small library have been written, talked excitedly of a forthcoming novel about Massachusetts textile workers - "Call the Darkness Light," by Nancy Zzaroulis - on which she's been working as an editor for Double day.

Jules Feiffer spoke of his screen play for a new show about Popeye.

Galbraith said he was afflicted by "the old Somerset Maugham syndrome. Until 50 writing is hard work. Then it becomes compulsive."

Weymouth, wearing a flowing red chiffon dress, welcomed her guests with brief remarks dictated to her, she said, "in a sexist move" by Schlesinger.

Among the guests who came to help the library get better known in its effort to attract money and archival material were John Chancellor; the founder of the American Civil Liberties Union, Roger Baldwin; Former Commerce Secretary Peter Peterson; philanthropist and author Philip Stern; Mary Lasker; Katharine Graham, Washington Post board chairman and mother of Weymouth; Jean Vanderbilt, Ahmet Ertegun of Atlantic Records and Newseek Editor Ed Kosner.

Form envelopes with pledge cards were distributed to the guests, and New York's Rep. Elizabeth Holtzman, a Radcliffe graduate, announced that she is giving her papers to the Schlesinger Library.

The news of her donation was received warmly by the library's director, Patricia King. The party was, King said, the first effort the library has made to raise funds since it was founded in 1943.

Among its shelves, she said, were papers from women such as Harriet Beecher Stowe and Susan B. Anthony. The library also subscribes to magazines of interest to women or about women - including the Ladies Home Journal and a karate magazine, appropriately titled Black Belt Women. CAPTION: Picture, Jacqueline Onassis and Arthur Schlesinger by Donal F. Holway