“Streep has not cared about anything she has done in a long time as much as this, she says. “Because the material embedded in it is a lot of what I’ve been thinking about. The themes in the film, which I don’t feel like underlining, have interested me for a while. And you never see these subjects covered in films normally, and so that was very thrilling.” What subjects? I ask, picking up my underlining pen—women? Power? “Women and power and diminishment of power and loss of power,” she says. “And reconciliation with your life when you come to a point when you’ve lived most of it and it’s behind you. I have always liked and been intrigued by older people, and the idea that behind them lives every human trauma, drama, glory, jokes, love.” She was close to her grandmother, and remembers her saying that her husband, Streep’s grandfather, would be out playing golf when the school-board elections would come up. “My grandmother didn’t give a damn about politics, but she really cared who was going to be on the school board, and she would go out, interrupt him on the eighth hole, and give him a piece of paper with the names of the candidates on it and tell him who to vote for—but she was not allowed to vote. She was not allowed to vote for dogcatcher in her town, never mind president. Never mind imagine being president.”

She has played so many roles in the 35 years of her movie career. She never was an ingenue; when her first film came out, in 1977 (Julia, with Jane Fonda and Vanessa Redgrave), she was 28. In the eighties, the era of Reaganomics and Thatcherism, she made huge movies in a Babel of accents and dialects: The French Lieutenant’s Woman, Sophie’s Choice, Silkwood, Out of Africa, A Cry in the Dark. In 1989, she turned 40. “I remember turning to my husband and saying, ‘Well, what should we do? Because it’s over.’ ” The following year, she received three offers to play witches in different movies. She saw the subtext pretty clearly: “Once women passed childbearing age they could only be seen as grotesque on some level.” But with The Bridges of Madison County (1995) she captured “the audience that were my girls, that I knew they’d get it if we could get the movie made,” hence Dancing at Lughnasa and One True Thing, which were also about “women whose usefulness had passed.” And her last five years saw hit follow hit: The Devil Wears Prada, Mamma Mia!, Julie & Julia, It’s Complicated. That last film, she says, “in the period of Silkwood, could never have been made, with a 60-year-old actress deciding between her ex-husband and another man. With a 40-year-old actress it would never have been made.”

Now she’s 62, playing Margaret Thatcher—from 49 to 85—and the cover star ofVogue. She has such a big laugh bubbling under her serene expression that it finally bursts out as I duck around the o word: “I was joking with the ladies earlier,” she said (when they were having their picture taken). “And I told them I was probably the oldest person ever to be on the cover of Vogue.””

Read Vicki Wood’s full interview with Meryl Streep on Vogue.com and  in Vogue’s January 2012 issue, coming soon.