McGranger was originally a primary school teacher who trained at the Riverina College of Advanced Education in Wagga Wagga, New South Wales in 1975 where she had her initial actor training. She started her career in stage roles, early roles included Rose in Bye Bye Birdie and Anita in West Side Story. After further experience with the Q Theatre in Penrith, west of Sydney, she started working in television and won a small part in soap opera The Flying Doctors.
She undertook her best-known role on 12 January 1993, when she joined the cast of Home and Away playing Irene Roberts. At first cast in a guest role, McGranger was made a permanent cast member on 7 October 1993. In 2014 McGranger overtook former co-star Kate Richie as the longest serving actress to play the same character in Australian television.
McGranger was a participant in the fourteenth season of Dancing with the Stars. She regularly appears in British pantomimes during the Christmas season, and has starred in pantomimes in Brighton, Torquay, York and Ashton-under-Lyne and Southport.