"We haven't eaten a canned vegetable in the last seven years." Ruth Beebe Hill, rugged individual, linguist and hard-working writer, pauses at a buffet table, looking quizzically at the vegetables and thinking about a faraway garden.

Hill's epic Indian novel, "Hanta Yo," 30 years in preparation and 834 pages long, is in its fourth month on the best-seller lists, and she is out beating the drums to help it along.

Although she has been on the promotional road since January, and despite her 66 years, Hill's thin, sinewy frame shows no signs of fatigue. She sits ramrod-straight, declines a cocktail before lunch, and her conversation ricochets from Indian languages to living off the land on San Juan Island, near Seattle.

"We have this huge garden back home," she says. "My husband planned it as one of the joys of his retirement. He was a cancer researcher and made some important discoveries in the field of enzymes. He does his gardening scientifically and we could feed the whole island with the vegetables we get."

That kind of self-reliance has infused Hill's life - and her novel as well. "One reviewer, she says, "summed it up four words: 'Ayn Rand meets Hiawatha.' What can you say about that? Well, perhaps it's about time Ayn Rand met Hiawatha - but of course Hiawatha is a myth, and I wrote about real people."

Of course, the Indians in Hill's novel are very individualistic people. But that is only one reason why the author was attracted to them. In fact, Hill has read "The Fountainhead" 17 times and once adapted it for the stage.

"Actually," she muses, "that reviewer had no idea of how close he was to the truth."

"I first read 'The Fountainhead' in 1945 because one of my friends who didn't even know Ayn Rand was a woman told me, 'He used you as the prototype for Dominique.' I kept reading the book, wondering why my friends - and others, too - would see me as a prototype. I guess it's because my own personality is strong."

So is her curiosity. She became interested in Indians originally because of a remark her father made one Thanksgiving Day before she was 10 years old. "He told us about an English-speaking Indian named Squanto who was the first to greet my ancestor, Francis Cooke, when he arrived on the Mayflower. Then, when I was a freshman at Oberlin, there was a girl in my dormitory whose name, as I recall, was Amelia Walking Stick, and she added to my interest in Indians."

It remained, however, one interest among many. She was the first girl to edit her high school newspaper. After that, "I wanted to experience as many things as I could, so when I went to college I decided to major in geology - the earth - and minor in astronomy - the sky. Since then, I've been filling in between."

At 24, she was lecturing on evolution at the University of Mississippi and later even did a bit of free enterprising. "In Denver, while my husband was working for his doctorate, I opened a bridal business. I thought, 'I like being around happy people, and who is happier than brides?" You'd be surprised."

But Indians have her main preoccupation for the last 30 years. "The Dakotah had a remarkable civilization.While they were tramping aroung the plains, chasing buffalo, they were also translating Shakespeare into the classic Dakotah language."

In three decades of research on "Hanta Yo," Hill intereviewed some 1,000 Indians and read every ethnological study ever published on the Dakotah tribes (approximately 2,500 publications). The projects, she says, began in 1949 when Hill drove from Virginia to California, "moving west cross-country and stopping at every place where there were Indians and where we would not be intruding."

Her story traces the lives of two families of the Mahto band of Teton Sioux from 1769 (when they are still living in an essentially pre-Columbian style) to 1834 (when the presence of the white man is beginning to be felt as traders and missionaries begin to encroach on the Central Plains).

The book is written from inside the mentality and language of pre-Columbian Indians, creating on the page not merely a special vocabulary and exotic scenery and action, but a whole world-view outside the Hebrew-Greco-Roman patterns of thought that we take for granted.

"Pre-Columbian Indians," Hill says, "could not conjugate the verb 'to think' except in the first-person singular. How can I say what anyone else thinks? And they had no subjunctive, because they spoke about what was here and now."

Creating this effect was the hardest part of the writing, Hill says. Since 1964, she has been collaborating with Chunksa Yuha, one of the last living inheritors of the Dakotah oral tradition. Now 74, he is the only surviving member of a group of eight children, born on a reservation in Nebraska, who were taught the ancient language and not allowed to learn English until their teens. Working together, he and Hill translated the entire novel into the archaic language (and its thought-patterns)then back into 19th-century English.

A labor of love? "It's a labor of respect," Hill says. "If respect if love, then it's a labor of love."

She begins her introduction to cHanta Yo" with a long list of words that were not in the archaic Indian languages before the coming of the white man: "Admit, assume, because, believe, could, doubt . . . mercy . . . promise . . ."

"Did you know," Hill asks over lunch, "that the world 'thunderbird' does not exist in any Indian language? And the expression that is usually translated 'Great White Father' is actually a Dakotah expression meaning 'the people permit him to call himself grandfather.'"

With "Hanta Yo" on the best-seller lists, Hill has completed the second part of the three-part ambition formulated early in her life: "I wanted a boy, a book and a bookstore," she recalls. Her son, Reid, is now 35 years old.

The rest should be easy. CAPTION: Picture, Ruth Hill, by Frank Johnston