Judy is in theaters September 27
The 50-year-old star stars as Garland as she arrives in London in the winter of 1968 for a series of sold-out concerts despite her exhaustion and deteriorating health. Garland died of an accidental barbiturate overdose months after the tour ended in June 1969 in London. She was 47.
The film is an adaptation of the Tony Award-nominated Broadway play End of the Rainbow by Peter Quilter.
To prepare for the role, the Oscar winner took music lessons, studied choreography and read up about the actress and singer, who shot to fame in 1939 when she played Dorothy in The Wizard of Oz but struggled later in life.
The Bridget Jones star spent two hours a day in the makeup chair getting prosthetics, contact lenses and wigs applied.
“It was an exercise in Zen for sure,” she tells PEOPLE.
Zellweger says getting the chance to play Garland was a “magical” experience.
“It was such a joy learning about the magnificence of this person,” she says. “I always admired her. She was so quick and so funny. She could hit the ball back with the best of them.”
In addition to Zellweger in the title role, the film stars Finn Wittrock as Garland’s fifth husband Mickey Deans, Rufus Sewell as her third husband Sid Luft and Michael Gambon as her manager Bernard Delfont. Bella Ramsey plays Garland’s daughter Lorna Luft while Gemma-Leah Devereux plays her daughter Liza Minnelli.
Minnelli, 73, made it clear she did not support the biopic in a statement on her Facebook page in June 2018 after inaccurate reports that she had met with Zellweger.
“I have never met nor spoken to Renee Zellweger… I don’t know how these stories get started, but I do not approve nor sanction the upcoming film about Judy Garland in any way. Any reports to the contrary are 100% Fiction,” Minnelli wrote.
Judy is in theaters September 27.