WITH AN EYE ON . . . : Christine Baranski’s flair for bravado makes her a perfect pal on ‘Cybill’

It’s the run-through rehearsal for the season finale of “Cybill” at CBS’ Studio Center in Studio City, and there’s Christine Baranski crawling inside a rather large metal tube.

Those who’ve been watching the sitcom since it spiced up CBS’ midseason lineup with its bawdy inside-Hollywood humor won’t be surprised to learn it’s just Maryann Thorpe (Baranski) on another mission of terror against her ex-husband. This one involves putting Limburger cheese inside the ex’s home air duct--with the star of the show, Cybill Shepherd as best friend Cybill Sheridan, along for the prank.

The scene over, Baranski extricates herself from the tubing and sings, “I’ve Never Been in Duct Before” to the tune of “I’ve Never Been in Love Before” from “Guys and Dolls.”

“I can’t say I’ve ever acted in an air-conditioning duct before,” she tells an amused visitor. “But this is the reason you do television.”

The two-time Tony Award winner (for Tom Stoppard’s “The Real Thing” in 1984 and Neil Simon’s “Rumors” in 1989) has been winning raves for her first stab at series television. She made the move after years of wooing by Marcy Carsey and Tom Werner, two of the executive producers of “Cybill.”

“I met Marcy when I won the Tony for ‘Rumors,’ ” she recalls. “Tom and Marcy approached me in such a caring way and said, ‘We really want you.’ I thought, ‘If I do television, I’d want to be in their hands.’ ”

Baranski was the first actress to read for the role of Maryann, the martini-swigging (often from her gym water bottle) ex-wife of a plastic surgeon whom she sometimes refers to, with a curl of the lip, as “Dr. Dick.”

“She hit it out of the park,” says executive producer Chuck Lorre, who created the show. “We read others because we couldn’t believe our good fortune, and we thought it would be prudent to read them. But she understood the character.”

Baranski credits her theater background, which also includes Drama Desk awards for her performances in “The Real Thing” and Terrence McNally’s “Lips Together, Teeth Apart.” She was also in the Broadway productions of David Rabe’s “Hurlyburly” and John Guare’s “The House of Blue Leaves.”

“I come to this after 20 years of doing flamboyant women on stage,” she says. “Maryann is theatrical. She has a lot of flair. You can’t hold back with this character. You have to bring a bravado to her, and because I’d done so many (similar characters) on stage, I’m not intimidated by her. It’s a perfect match of character and actress, a wonderful symbiosis.”

Baranski, who has also appeared in the TV movies “To Dance With the White Dog” and “Playing for Time,” bases Maryann on a friend whom, she says, “is one of the wittiest people I’ve ever met. Yet for all her intellect, she’s vulnerable. People respond to Maryann’s humanity, her sense of humor, and that brio. They wish they had that audacity--you don’t see it in real life.”

Baranski’s own real life bears little resemblance to Maryann’s. “My home scene is very strong,” she says. She lives in rural Connecticut with her husband of 11 years, actor Matthew Cowles--best known for his turns as the rascally ex-pimp Billy Clyde Tuggle on the daytime soap “All My Children”--and their two daughters. She also maintains a New York apartment.

Commuting from Connecticut is about the only downside to her new job. “I was delighted at how much I’m enjoying working,” she says. “I didn’t realize how fond I’d be of virtually everyone on the set. Cybill and I really hit it off. We don’t have to pretend to be friends. Even at the get-go, she was just a woman I instantly adored.”

The actress, whose feature credits include “Reversal of Fortune,” “Legal Eagles,” “Addams Family Values” and “The Ref,” will next be seen in the movie version of Paul Rudnick’s “Jeffrey,” a comedy about AIDS, due out in August. Later this month she films “Birds of a Feather,” starring Robin Williams.

Maryann, though, remains near to her heart. “I do think there’s something really attractive and thrilling about this 42-year-old woman in a micro-miniskirt, blazing through life,” she says. “You don’t find her worrying about menopause.”

“Cybill” airs Mondays at 9:30 p.m. on CBS.