New York ? Christie Brinkley is back where she should be: in front of the camera as the face of CoverGirl.

Brinkley was a supermodel before there was such a word, and a large part of her popularity and recognizability came through 20 years of CoverGirl ads. (Her three Sports Illustrated swimsuit issue covers three years in a row, 1979-81, didn’t hurt, either.)

With her long blond hair, blue eyes and curvy-yet-athletic figure, her all-American looks made her the perfect match for the all-American cosmetics company. The association began in 1976 – before President Carter moved into the White House.

The two parted ways in the mid-1990s, but it was an “amiable separation.” Put it this way, she continued to use CoverGirl makeup, Brinkley says with a laugh.

When the company approached her earlier this year to rekindle their relationship, Brinkley didn’t blink.

After all, it’s fun work if you can get it, says Brinkley, who spent this day romping on the beach with her horse, dog and her two younger children, daughter Sailor, 7, and son Jack, 10, with the cameras rolling for the TV and print ads that break this week.

Christie Brinkley had a 20-year contract with CoverGirl, then a 10-year hiatus. Now she's back to pitch a line called Advanced Radiance for the company.

“We’ve been having a ball today. It’s like a time warp. It’s as if those 10 years between never happened,” she says by cell phone from the shoot in the Hamptons on Long Island, N.Y.

Of course, what is different is that Brinkley is now 51 and she’s pitching a line called Advanced Radiance, anti-aging makeup intended for women 30 and up.

“There is such an age phobia in this country, and this ad is showing me being comfortable with the age I am. I think it’s a good positive image, something you don’t see enough of. … CoverGirl is making an effort to show a wide range of beauty – different ethnicities and age groups,” Brinkley says.

Indeed, Brinkley joins a company stable of models that also includes Queen Latifah, Elsa Benitez, former Miss Universe Amelia Vega and Molly Sims, who picked up where Brinkley left off as the healthy, fun-loving beach type.

“Christie embodies our strong heritage: She’s clean, fresh, natural, a good girl with a wink, and has a fun-spirited look. She’s the quintessential face of that, but the 2000s vs. the 1970s are different. The world is more diverse today,” explains Anne Martin, the vice president of global cosmetic and beauty marketing for CoverGirl parent company Procter & Gamble.

Brinkley did do some modeling in the intervening years – most recently a runway appearance in a slinky red spaghetti-strap gown during a charity fashion show in February – but she says she devoted much of her down time to raising her children. Her oldest daughter, 19-year-old Alexa, whose father is Brinkley’s ex-husband Billy Joel, is headed to college this fall.

The biggest change in Brinkley’s beauty routine as she’s aged is less sun, more SPF.

Christie Brinkley is returning as a CoverGirl model, but this time it's a family affair with daughter Sailor and son Jack.

“At 30, I said, ‘OK, I’ve had enough sun.’ … I now use makeup for a healthy-looking glow because a real one isn’t that healthy,” says Brinkley, who was raised in seaside Malibu, Calif.

She uses a suntan-colored blush with a dab of pink cream blusher on top.

Both her daughters are into makeup, too. “When you paint a little girl’s toenails for the first time at 3, it’s a bonding thing,” Brinkley says.

“Her public perception as a mother is very strong,” says Andrew Sacks, president of AgencySacks, a Manhattan-based advertising agency that concentrates on the upscale market.

“People like her. There’s not a diva association. For a very wholesome American brand, it’s a perfect match,” he adds.

After being featured on more than 500 magazine covers, Brinkley says people see her as approachable – and that’s her greatest asset as a model.

“I think the brand of celebrity that I have is that people just feel like I’m their friend, that they know me and people have a tendency to just walk right up and tell me stories like, ‘You and I were pregnant at the same time,”‘ she says.

“After so many years of being around, people see me on the street and say, ‘Hey Christie, how you doin’?’ or ‘Hey, looking good!”‘