Neiman-Marcus may be more their style, but there they were, 48 wealthy Houston women, crammed into J.C. Penney's for a peek at Halston's new ready-to-wear line. But the real lure may have been less the fashions than the show's narrator, Barbara (Mrs. Cary) Grant.

Before this, her debut as a clothes-caster, the former Barbara Harris, 33, sat in a lingerie storeroom at Penney's trying to ignore the discomfort of a two-day-old root canal and supressing stage fright. "I see no reason to be nervous," she assured herself. "If I mess up I don't think anybody will kill me."

No problem. For 60 minutes Barbara wowed the well-heeled likes of Joan Schnitzer and Carolyn Farb with her crisply delivered description of 32 outfits (retailing from $38 for men's-style pajamas to $200 for a wool crepe suit.)

Barbara has no illusions about why she was engaged to narrate two shows (the other was last week in Sacramento). "If I were just Barbara Harris and not married to Cary," admits the fifth Mrs. Grant, "I don't think I would have been asked to do it." Barbara gave up a public relations job two years ago when she married the star. Before they wed, she had been worried about the 46-year age difference between them. "I knew how much I could love him," she says, "and I didn't want the hurt of what might happen in the future. Then gradually, because we enjoyed each other so much, I realized how important it was to take what happens."

Nevertheless, she wanted to resume working at least part-time. J.C. Penney's approached Barbara because, says a store spokesman, she "typifies the new woman today who appreciates fashionable designs at a believe-able price." Halston agrees: "I think Barbara has style and panache."

Still it seems ironic that, after marriages to three American actresses (Virginia Cherrill, Betsy Drake and Dyan Cannon) as well as Woolworth heiress Betty Hutton, debonair Cary would wind up with a nice British working girl. Actually, Barbara hails from Dar es Salaam, Tanzania, where she was the youngest of three daughters of British Provincial Commissioner James Harris. At 10, she was sent to school in England. The next year her father returned home, later bought a farm in Devon and enrolled his girls in day school there. "At that age" remembers Barbara, "moving to the country did not appeal to me in the least."

In 1969 she attended secretarial school in London and after graduating worked as a temp. "I couldn't decide what to do," she admits. Hired in 1971 as a secretary for a textile firm, she tried her hand in the design department, helped put on fashion shows and eventually landed a public relations job at London's Royal Lancaster Hotel. It was there, in 1976, that she met Grant. "I wasn't in awe of him," she says. "I tend to see the person, as opposed to the name."

Barbara's straight forward approach must have charmed the worldly-wise screen legend, but they remained "just friends" for two years. When the romance bloomed, Cary took her on a tour (Reno, Las Vegas) for three weeks in 1978 to see if she could adjust to life in the United States. "Of course, I loved it," Barbara says, "because I loved him."

Her burgeoning career as a Penney's fashion symbol is a natural for Barbara, who sews her own evening gowns and makes the cotton caftans her husband wears around the house. "They're cool and comfortable," she says.

The Grants have just settled into a new home in Los Angeles. Although Cary hasn't made a film in 18 years, he still gets too much mail for Barbara, who sometimes doubles as his secretary, to answer. On weekends they often empty their nest of the servants (one full-time housekeeper and five part-timers). "We like to have the place to ourselves," she says—except when Jennifer, Cary's 17-year-old daughter by Dyan Cannon, visits. A freshman at Stanford University, Jennifer has become her stepmum's buddy. "I adore her," says Barbara, who likes to whip up massive English breakfasts of bangers and mash (sausages and mashed potatoes).

Barbara's winter-spring romance has its advantages. "We don't argue over ridiculous things," she notes. "We appreciate each other more than a younger couple because time," she adds thoughtfully, "is so precious."