The veteran actress plays U.S. culinary queen Julia Child in the new film, which was written, directed and produced by Nora Ephron.
Streep was unaware of her pal's project until they met up in New York - and the 60 year old proved her star credentials with an unexpected audition piece.
Ephron says, "I was at the theatre one night, Shakespeare In The Park in New York Central Park, and I saw her (Streep) and she said, 'What are you doing?' and I said, 'Blah blah blah... Julia Child' and she immediately rose up. Julia was six (foot) two (inches), Meryl five-six and she suddenly grew in front of me and went into this Julia thing, this warble thing of Julia.
"I thought to myself, 'Well, that's the end of that casting search.' It seemed to me she was auditioning for it. It's as close as you'll get to Meryl Streep auditioning."