Meryl Streep and Sean Penn Photo by: Kevin Mazur / Wireimage; John Shearer / Wireimage
Meryl Streep, Sean Penn Win Lead SAG Awards | Kate Winslet, Sean Penn
The Screen Actors Guild shared the wealth among this year's biggest stars, showering Sean Penn and Meryl Streep with leading actor awards during the live telecast Sunday.

Streep humorously acknowledged her surprise while accepting the award for outstanding female actor in a leading role for Doubt. "I didn't even buy a dress," said the actress, who wore black pants. "I'm really, really shocked."

(Click here to see the night's Best Dressed Stars!)

But Streep, who was beat out in the leading actress category by Kate Winslet at the Golden Globes, used her time at the podium to make a serious point.

"There is no such thing as the best actress," she said. "There is no such thing as the greatest living actress. I am in a position where I have secret information that I know this to be true. I am so in awe of the work of the women this year – nominated, not nominated – so proud of us girls. Everybody wins when we get parts like this."

Best in Film

If Sunday's victories were any indication, those leading stars would be wise to prepare Academy Award acceptance speeches.

With 15 categories recognizing acting achievement on television and in the movies, the SAG Awards – which are voted on by the union celebrating actors and are broadcast from Los Angeles's Shrine Auditorium – are considered by many in the industry to anticipate Oscar winners.

Honored for his role as Harvey Milk in the biopic Milk, Penn poignantly noted that "as actors, we don't play gay/straight ... we play human beings." Said the star: "This is a story about equal rights for all human beings." (Penn's victory comes after The Wrestler's Mickey Rourke has picked up leading actor wins at various other ceremonies.)

Another big winner: The cast of Slumdog Millionaire was named outstanding cast in a motion picture, foreshadowing a probable Best Picture Oscar win.

Supporting Stars

A favorite this award season, Kate Winslet was named best female actor in a supporting role for her part in the Holocaust drama The Reader. Already a double Golden Globe winner, the actress was overwhelmed by her early honor. "It's really an honor to be included in what, I think, is such a remarkable year [in film]," she said.

In the supporting male category, Heath Ledger earned another posthumous trophy for his role as the macabre Joker in The Dark Knight. "I'm quite emotional," said castmate Gary Oldman, who accepted the award. "He was an extraordinary young man with an extraordinary talent, and it is wonderful that you have acknowledged that." (Ledger was nominated for an Oscar for the role on the first anniversary of his death.)

Alec Baldwin Photo by: Kevin Winter / Getty
Meryl Streep, Sean Penn Win Lead SAG Awards | Screen Actors Guild Awards 2009, Alec Baldwin

30 Rock Sweeps

Meanwhile, another leading lady, Tina Fey, had a big night, too. The 30 Rock star earned the outstanding female actor award, while the show took home the best ensemble comedy series.

Fey collected the evening's first award and dedicated it to her daughter Alice, whom she called "the funniest person in my family." The actress has been on an award-show roll: She also recently nabbed a Golden Globe for the same role.

In another Golden Globe redux, Fey's 30 Rock castmate Alec Baldwin picked up the evening's second award, male actor in a comedy series. "I get to do this show with a bunch of people who are just the funniest and sweetest people," said the actor, who brought his daughter Ireland as his date for the evening. Soon, Baldwin was joined by his costars, as they joyfully accepted the ensemble in a comedy series award.

Dramatic Wins

It was also a big night for AMC's Mad Men. The show earned best ensemble in a drama series, and leading actor Jon Hamm lightened the moment. He referenced the show's ratings struggle by thanking its "dozens of viewers."

For the second consecutive year, Hugh Laurie was named best male actor in a drama series for his role as a cantankerous doctor on House – and the Brit was anything but dour at the podium. "I actually had $100 on James Spader [winning]," he said. "This is just not my night!"

Click here for a complete list of the night's winners.