After every performance of Wicked, Donna McKechnie opens the Gershwin Theatre stage door and is greeted by countless screaming fans. The enthusiasm she feels from people of all ages for this show is reminiscent of what she felt following performances of another iconic musical nearly 50 years ago.

“I’m so gratified to see how they appreciate it. I used to get that response in A Chorus Line. People would come up and say, ‘This is life-changing,’” the Tony Award-winning actress, who starred as Cassie in A Chorus Line back in 1975, tells Broadway Direct.

For the first time in nearly 30 years, McKechnie is back on the Broadway stage. She stars as Wicked’s Madame Morrible, the head of Shiz, where Glinda and Elphaba, played by Alexandra Socha and Mary Kate Morrissey, respectively, attend school. The musical, based on the novel by Gregory Maguire, tells the story of what happened before Dorothy followed the yellow brick road.

“I’m having the best time of my life,” McKechnie says enthusiastically, noting the three-decade gap on her Broadway résumé. “I’ve been in big shows, but not this big!” She was last seen on stage in State Fair back in 1996. She was also the standby for Chita Rivera in The Visit in 2015, but never went on.

The role came out of the blue for the Promises Promises star. McKechnie was performing her Stephen Sondheim concert revue in Palm Springs, California, when director Joe Mantello went to see her in it. She says she heard that the creative team later held a meeting to discuss potential stars to step into the role and her name came up, “only because he had just seen me,” she says. When her agent called with the job offer, she was surprised. “I was excited because the idea was great.”

The first task at hand was to see the musical again to refresh her memory, since she saw it with the original cast when it opened in 2003. “I [had] to just see if I can do it. It’s been a long time since I did eight shows a week, which, nobody knows what that’s like unless you’ve done eight shows a week,” she says.

This time, it was a much different experience.

“I sat there with a different frame of reference, a different point of view, and a different intention,” she says of being in the audience studying the actress then playing Madame Morrible.

Once she accepted the part, she went to work preparing, which included singing lessons with her vocal instructor, Deric Rosenblatt, and doubling her Pilates sessions in order to build stamina.

McKechnie says her interpretation of Morrible is that “she’s kind of from the other side of the tracks, and has been humiliated in her life. The written page indicates that she’s very ambitious and manipulative. But she wants power. She knows that she’s somewhat inadequate. She wants a way out of this. She wants to be in charge. She wants to be in command and she’s going to manipulate other talented people.”

Many fans ask at the stage door what it’s like to play the evil character — which shouldn’t be a spoiler since the show’s been around for so long. “It’s her humanity” is often McKechnie’s response, but she was stumped on how to explain that to a 9-year-old the other night. “It’s been producing that hurt, that anger, and it’s layered into that rage. That’s how she acts out, and then she goes kind of demented.”

When McKechnie is off-stage, she’s amazed at the action happening backstage. “The theatre is so big. There’s a whole other show going on behind the scenes with the crew and the dressers. Everyone has to be choreographed with all of their travel. They can’t change their pattern of travel; it might collide with a dresser or a big barrel of costumes.”

For her, there have been two hurdles. One: the shoes. She is quick to point out that’s been the hardest part of the return to Broadway. Her feet were in such discomfort that she turned to the head of the wardrobe department, Alyce Gilbert, who also worked on A Chorus Line, and found fabric shoes that pair with her costumes. “I started wearing them and everything was brilliant.” The other pain point has been the theatre’s raked stage. Only a few of the Broadway theatres still have slanted stages, where it’s higher upstage than downstage. “It’s daunting. You’re standing there and you just feel like you could fall over. It looked like I was going to be running down a hill, it was so slanted.”

But despite the raked stage, “that was the kind of the thrill and excitement for me to be in that situation,” and one of the reasons for her return to Broadway from “semi-retirement.”

For the past few years, she’s been enjoying performing in regional productions in addition to her concerts around the country where she sings songs she’d never have the opportunity to do in full-scale musicals. She was sent scripts here and there, but wasn’t in love with them. When asked why it took so long to return to Broadway, McKechnie replies candidly: “Honestly, there weren’t any parts available for me. I wasn’t getting offers, and even auditions were hard to come by at a certain age. I wasn’t eager to get back to doing a Broadway show unless it was really good. As a woman, as an actor, as you get older, there are fewer and fewer parts that are good.”

With all the endorphins from doing Wicked, she’s since made a list of possible roles in plays from The Gin Game to Driving Miss Daisy — all while getting ready to celebrate the 50th anniversary of “One Singular Sensation.” For that, she’s counting on Baayork Lee, the original Connie in A Chorus Line, to organize a celebration. “I told her I will avail myself to whatever she wants to do,” McKechnie says.

“[A Chorus Line director] Michael [Bennett’s] legacy is still changing lives. I haven’t had that kind of experience with people responding to [a show I’ve done] until Wicked, honestly. It’s like a different version of A Chorus Line that had a great life and always played somewhere and has gone all around the world.”