TORONTO -- There's glitz, glamour and reinvention on parade at this year's Toronto International Film Festival, where Hollywood heavyweights including Sandra Bullock, Matthew McConaughey, Daniel Radcliffe and Jude Law are among the stars unleashing radical roles that recast their well-worn images.

Challenging performances will mark this year's fest, predict programming bosses Piers Handling and Cameron Bailey, who touted a celeb-packed lineup including Meryl Streep, Colin Firth, Julia Roberts, Benedict Cumberbatch, Kate Winslet and Jennifer Aniston.

Streep and Roberts lead an "an actor's showcase" in the family drama "August: Osage County," sure to be one of the hottest titles when films begin unspooling Thursday.

"And they're all just at the top of their game," Bailey says of an ensemble rounded out by Ewan McGregor, Sam Shepard, Chris Cooper and Cumberbatch.

"It's got really meaty dialogue, great characters. I think those performances will definitely be noticed."

Envelope-pushing performances are expected from McConaughey and Jared Leto in the "Dallas Buyers Club," for which both "underwent remarkable physical transformations," says Bailey.

McConaughey reportedly shed nearly 40 pounds to play heterosexual HIV sufferer-turned-activist Ron Woodroof, resulting in a rail-thin frame that couldn't be further from his "Magic Mike" physique.

Leto, meanwhile, dons lipstick and hose for his role as a desperate drag queen. Quebec director Jean-Marc Vallee helms the '80s-set drama, and is one of several Canuck filmmakers with U.S.-backed ventures this year.

In other left-field offerings, Bullock trades her rom-com reputation for the sober sci-fi drama "Gravity" directed by Alfonso Cuaron; Jake Gyllenhaal goes arty and surreal for Denis Villeneuve's mysterious "Enemy;" and Joseph Gordon-Levitt graduates to multi-hyphenate mover-and-shaker with the romantic comedy "Don Jon," which he wrote, directs and stars in as a muscle-bound porn addict.

Brits figure heavily elsewhere, with Chiwetel Ejiofor leading a broad cast for the period drama "12 Years a Slave;" Cumberbatch going platinum blond for Thursday's opening film "The Fifth Estate," about WikiLeaks founder Julian Assange; and Idris Elba appearing to master an impression of South African hero Nelson Mandela for "Mandela: Long Walk to Freedom."

"This is a British actor who gets the physical bearing of Mandela, and especially his voice, in quite a remarkable way," Bailey gushes of Elba.

Meanwhile, Winslet is a depressed single mother caught off guard by an escaped convict in Jason Reitman's "Labor Day," Law turns in an "outrageous performance" as a gangster just released from prison in "Dom Hemingway," according to Handling, while Judi Dench delivers "one of the best performances she's ever given" in Stephen Frears' film "Philomena."

"Very strong female performances, I think, this year," Handling notes.

Then there are the over-achievers -- several performers have three films at the fest, which is widely regarded as a key platform for Oscar hopefuls.

Mia Wasikowska lays out her chops in the Australian period drama "Tracks" with "Girls" star Adam Driver; the surreal comedy "The Double" co-starring rumoured boyfriend Jesse Eisenberg; and Jim Jarmusch's vampire tale "Only Lovers Left Alive," starring Tilda Swinton.

Radcliffe, meanwhile, attempts to shed his magical past with a trio of his own: as a man reeling from his girlfriend's mysterious death in "Horns;" as beat poet Allen Ginsberg in the period drama "Kill Your Darlings;" and as a beleaguered romantic suitor in the Canadian-Irish co-production "The F Word," helmed by "Goon" and "Fubar" director Michael Dowse.

"We all know Daniel Radcliffe from the Harry Potter films, he has really made a very clear effort to move well beyond Harry Potter," Bailey says of the distinctly adult fare.

"We have three films with Daniel in them this year ... playing all very different characters and none of them at all cute and wizardly."

But when it comes to potential breakthroughs, Bailey crowns Cumberbatch "man of the festival" for appearing in three especially hot titles, starting with the timely WikiLeaks feature "The Fifth Estate," which earned early notoriety when Assange slammed it for being a "propaganda attack."

The "Sherlock" star will also be seen in "12 Years a Slave" and "August: Osage County," leading Handling to predict an impending "breakthrough as a major star."

Canucks on the cusp of cross-border glory could include the Oscar-nominated Villeneuve, who hopes to make a splash with two films featuring Gyllenhaal: the big budget, studio-backed thriller "Prisoners," starring Hugh Jackman as a father hell-bent on finding his missing daughter, and the Canada-Spain co-production "Enemy," with Gyllenhaal as a Toronto professor obsessed with a man who appears to be his exact doppelganger.

Friend and "Enemy" co-producer Luc Dery says the double features should double the spotlight on the generally low-key Villeneuve, best known for intense, dark, lyrical meditations.

"For Denis' profile I think it's pretty incredible," says Dery, also one of the producers on Villeneuve's Oscar-nominated saga "Incendies."

"He's going to be one of the directors to watch in the festival and at a festival like Toronto it's pretty major."

Don McKellar's feel-good comedy "The Grand Seduction," meanwhile, promises plenty of cross-border appeal, thanks to leading turns from Irish star Brendan Gleeson and "Friday Night Lights" hunk Taylor Kitsch.

It doesn't hurt that the script is adapted from the Quebec hit "La grande seduction," and according to McKellar, features scene-stealing turns by Gordon Pinsent as a boozy fisherman.

Whether it's shifting from boy wizard to romantic lead, jumping from a rom-com past to sci-fi existentialism, or delivering a weird psychological thriller alongside a big-budget studio blockbuster, Toronto is a good place to try out radical new ventures, says Bailey.

That's largely because of its film-loving audiences, known for being warm, intelligent and up for a wide range of fare, from an offbeat horror flick, to a foreign-language experimental offering and the mainstream tent-pole.

"It's really become known as one of the most informed, smartest, most enthusiastic film audiences in the world and how a film plays here can tell you a lot about what kind of life it's going to have after the festival," says Bailey.

"That's a unique quality that I think our festival has as one of the leading public festivals in the world. It's not just the movies, it's how they react in that alchemical way with the audience here."

Other big titles include Atom Egoyan's look at the infamous West Memphis Three case "Devil's Knot," starring Reese Witherspoon and Colin Firth; the feature-film debut of "Mad Men" creator Weiner in "You Are Here" with Owen Wilson and Zach Galifianakis; and the Alice Munro adaptation "Hateship Loveship," featuring Kristen Wiig as a plain Jane who longs for love.

Louise Archambault's coming of age tale "Gabrielle," which won the audience prize at the Locarno film festival, also heads to Toronto. Its francophone star Gabrielle Marion-Rivard, who plays a young woman with Williams Syndrome and actually has the genetic condition, will walk the red carpet.

"She is a standout in the film and she gives such a brave performance in the film," says Dery, who produced the film.

"It's sort of a feel-good movie that touches peope very deeply and we're looking forward to showing it in Toronto."

The lineup also includes one of the last performances of James Gandolfini, who appears in Nicole Holofcener's comedy "Enough Said." The "Sopranos" star plays the love interest of a divorced woman played by Julia Louis-Dreyfus.

And late "Glee" star Cory Monteith appears in two films, including the ensemble drama "All The Wrong Reasons," as a department store manager, and "McCanick," as an ex-con who draws unwanted attention from a hot-headed cop, played by David Morse.

Bailey admits the untimely passing of both stars posed a delicate dilemma for programmers.

"The first question for us is: Do you want to show this film in September? Is that the right moment? And once we've crossed that hurdle then we begin to think about how we want to showcase the film," he says.

"But I think you know, in both of these cases, these actors were I think taken far too soon, it was a shock for all of us and luckily we have their work. So we're happy to present and we would do it in whatever way the filmmakers feel is best."

The festival will also feature the directorial debuts of Keanu Reeves with "Man of Tai Chi," Jason Bateman's "Bad Words" and Mike Myers, who brings the documentary "Supermensch The Legend of Shep Gordon."

The fest will close with director Daniel Schechter's "Life of Crime," featuring Aniston and Mos Def. It's based on an Elmore Leonard novel.

The 11-day Toronto International Film Festival starts Thursday.