Auditioning for her breakthrough role, Collette proved one determined actress. She announced to writer-director Hogan "I AM Muriel!" and offered a strong audition. Hogan resisted casting her, though, because she was too thin. Like any actor who wants a role badly enough, Collette began a supervised diet, gaining over 40 pounds. Her efforts paid off as she earned worldwide critical praise and an Australian Film Institute Best Actress Award. (Her contract also wisely included a provision for a personal trainer to help her shed the excess weight after filming.) Like Minnie Driver (who underwent a similar experience with her breakthrough in "Circle of Friends"), Collette found that people had difficulty matching her svelte self with her onscreen persona. Gradually, through a series of fine performances in a variety of films, she has proven to be one of contemporary cinema's finest actresses. Collette offered a moving interpretation of the youthful version of the title character, an eccentric who was confined to an institution by her cruel father, in "Lilian's Story" and was suitably tough as an incarcerated drug addict who proves to have a sweet singing voice in the comedy "Cosi" (both 1996). The actress headed to America to play the girlfriend of one of David Schwimmer's high school buddies in "The Pallbearer" and then traveled to England to undertake the role of Harriet Smith, the sympathetic protégé of Jane Austen's titular "Emma" (also both 1996) in Douglas McGrath's winning screen adaptation.

Adding to her gallery of characterizations, Collette proved effective as a timid office worker who longed for more than the life of a temporary worker in the ensemble comedy-drama "Clockwatchers" and essayed a British detective trailing jewel thieves in "The James Gang" (both 1997). One of her oddest roles was as an Australian named Diana Spencer who identifies with the British princess of the same name in "Diana and Me" (1997). What was meant as a witty romantic comedy took on a frivolous triviality after the tragic death of the real-life Princess of Wales. Collette bounced back as the brassy bottle blonde girlfriend of an ex-con who gradually comes to doubt herself in the Australian drama "The Boys.” She further proved her dramatic mettle as Mandy Slade, the American wife of a glam rock singer who recreates herself as a British party girl, in Todd Haynes' "Velvet Goldmine" (both 1998), While she seemingly was all wrong for Mandy, Collette bravely threw herself into the part and delivered a layered and complex portrait of a woman who loses a part of herself when her husband's career comes to an abrupt end. Yet another unconventional role followed as she was cast as a nun who works in a brothel in Peter Greenaway's "8 1/2 Women" (1999).

That same year, the chameleonic actress was once more cast against type as a struggling thirtysomething single mother of a psychic child (Haley Joel Osment) in the popular "The Sixth Sense.” Collette successfully conveyed both the character's nonjudgmental stance as well as her feelings of inadequacy. Her richly nuanced performance garnered her a Best Supporting Actress Oscar nomination. Collette started 2000 taking on the new challenge of starring in a Broadway musical. Cast as Queenie, a 1920s vaudeville performer, who with her on stage partner Burrs (played by Mandy Patinkin), throws the titular bash. Revealing her singing and dancing abilities, Collette proved a revelation to many. While she was lighting up the Great White Way, she was also seen in John Singleton's remake of "Shaft" which reunited her onscreen with "Velvet Goldmine" co-star Christian Bale.

Collette continued to be an in-demand performer who could casually straddle the line between star, character actress and supporting player. She had a memorable turn as a wife in the midst of a marital breakdown in the HBO telepic "Dinner With Friends" (2001), playing one of the four leading roles; added some emotional support as Ben Affleck's long-suffering gal Friday in "Changing Lanes" (2002); and was mesmerizing in her brief, one-scene turn in "The Hours" as a 1950s woman suffering with an inability to give birth - and some other secrets as well. But it was in the 2002 comedy "About a Boy" (directed by the Weitz brothers from Nick Hornby's bestselling novel) that Collette gave her best post-"Sixth Sense" work to date, as a British single mother struggling to raise her sensitive and precocious but geeky son (Nicholas Hoult), who tries to fix her up with his new friend, an unrepentant rogue in a seemingly permanent arrested adolescence (Grant).

Collette received glowing reviews for her role as a geologist who becomes entangled with an Asian businessman in the Aussie indie "Japanese Story" (2003) and was a welcome presence in the underappreciated comedy "The Last Shot" (2004) opposite Matthew Broderick and Alec Baldwin, but could definitely avoided lending her talents to Nia Vardalos' comedic misfire "Connie & Carla" (2004). She was much better paired with co-star Cameron Diaz in director Curtis Hanson's dramedy "In Her Shoes" (2005), which cast the actresses as tight-knit but polar opposite sisters—Collette the responsible attorney with low self-esteem, Diaz played the reckless, sexy party girl—who have a calamitous falling out and must slowly come to learn that they share more than the same size feet.

In “The Night Listener” (2006), an intense psychological thriller starring Robin Williams as a late-night radio host who develops a strong bond with an abused 14-year-old listener (Rory Culkin), Collette drew upon her past experiences for inspiration in playing a damaged mother who fakes ailments for attention (She was convincing enough in faking appendicitis that doctors actually removed the organ when she was 11-years-old.) Despite descent reviews, particularly for Collette’s fiercely creepy performance, “The Night Listener” faired poorly at the box office. Her next film, “Little Miss Sunshine” (2006), an hilarious black comedy with a heart about the cross-country shenanigans of a dysfunctional family driving 800-miles to whisk their 6-year-old daughter to a beauty pageant, Collette gave a strong performance as an out-of-her-wits wife and mother fed up with her husband’s (Greg Kinnear) pipedreams of becoming a famous inspirational speaker, while dealing with the attempted suicide of her brother (Steve Carell), a gay Proust scholar suffering after being spurned in love. “Little Miss Sunshine” emerged from the 2006 Sundance Film Festival as the obvious crowd favorite and went on to score with both critics and audiences, ramping up what may very well become an enjoyable awards season.