From mod to moderate: designer of the miniskirt goes domestic

English designer Mary Quant, like the Beatles, first acquired fame in the early 1960s as part of a youthful British cultural revolution that reverberated round the world.

Today, although she has long since left Carnaby Street and miniskirts behind, Miss Quant has lost none of her talent for combining colors and patterns in a style uniquely her own. She has continued to design fashions and cosmetics and, since 1970, department store lines of moderately priced wallpapers, paints, fabrics, bedclothes, and accessories.

Along the way, Queen Elizabeth recognized how broadly Mary Quant had changed the face of British design by bestowing on her the Order of the British Empire (O.B.E.). She was later designated a Royal Designer for Industry. In the late 1960's an exhibition of her designs called ''Mary Quant's London'' was held at the London Museum in Kensington Palace.

Her name may no longer ripple off a majority of tongues in the United States, but in England and on the Continent her reputation has never diminished. A recent British poll indicated that Mary Quant is practically a household word to 97 percent of the population. She far outscored all other popular designers, including Laura Ashley and Gloria Vanderbilt.

For the past year she has sought to reclaim the affections of Americans through a home-furnishings group called ''Mary Quant at Home.'' It features 11 licensees, including Wedgwood dinnerware, Bloomcraft fabrics, General Housewares ceramic cookware and serving pieces, Imperial wallpaper, and Contempo paper products.

Max Factor is now test-selling her line of cosmetics on the West Coast, and her stationery designs are going into stores across the country.

Sitting in the Chelsea headquarters of their design and business operations, Miss Quant's husband and business partner, Anthony Punkett Greene, recalls the early days of the Quant operation.

''We were art students when we decided to open a little shop called Bazaar on Kings Road, where we could make and sell Mary's fashion designs,'' he says, going back a quarter of a century. ''We thought at the time that we were speaking for an elite, artistic lot like ourselves, but actually we soon found we were speaking for a whole generation who wanted something fresh and new and who wanted to break with many staid, old-fashioned traditions. Of course, it was Mary's miniskirt that made headlines all over the world, and (the little shop) became the forerunner of Mary Quant Ltd.''

By the late 1960s, Miss Quant was beginning to find clothes boring. In 1970 she gave birth to their son, Orlando, now 13, and her interest turned instinctively to home and hearth. She began to focus on designing items for the home, where she used the same philosophy she had applied to clothes, which meant giving a great deal of style at affordable prices.

Now she is designing for the '60s generation grown up - people who, like her, are enjoying the pleasures of home and family, and whose tastes have moderated somewhat. Yet the biggest customers for the mood she produces are still in the 18-to-25 age range.

She says her basic approach to design is to include something romantic, something nostalgic, something old, and something absolutely new, then to blend them together with color and texture. Everything is coordinated. Right now she is moving into deeper, gray-tinted pastels and jewel tones.

''The '80s feel good to me,'' she says. ''People seem alive, young, forward-looking, and creative again.''

Once dubbed queen of the mods, Mary Quant still has the same piquant good looks, flapperish haircut, enigmatic smile, and dusky muted voice.

She and her husband and son are at home in England in what they describe as ''an Italian folly (a picnic place, in its original sense) with bell tower'' in the middle of Surrey, an hour's drive from London. His great-aunt lived there for almost 40 years, then willed it to them.

The house has, in her words, a ''comfortable, slightly battered, affectionate feel'' that is a blend of English chintzes, old and new pieces, all put together with loving and thoughtful abandon. The one thing the house isn't, she says, is a showroom of Quant designs, a final resting place of design samples or rejects.

Their second home is a 17th-century retreat in a small medieval village on the edge of the Alps, where France joins Italy. Its exact location is a Quant secret, but it, too, has a slightly battered feel, she admits, and is surrounded by a garden of old English roses. They travel there for three weeks in the summer and occasional weekends.

''My favorite kind of reading is cookbooks,'' the designer says, ''and I love outdoor winter picnics in our Surrey garden. We serve stews and pastas, and give people knitted rugs to bundle up in. We even run electric fires out through the window to take off the chill.''

Nigel French, the agent in New York who put together her American coordinated package of designs, describes the designer. ''Mary Quant is no prima donna,'' he says, ''and she takes the responsibility for every single design that comes out of her studio. She is very hard-working and attentive to detail.''

Various items in her collection are now at Bloomingdale's, Jordan Marsh in Boston, B. Altman's in New York, and the Broadway store in Los Angeles, among other stores. Japan has also become a prime market for designs by Mary Quant (particularly her bodywear), which means frequent travels to the Orient - an extension of her experience that delights her.