Grattan was educated in Kew, Victoria at Ruyton Girls' School. She completed a Bachelor of Arts at the University of Melbourne, majoring in politics, and then worked as a tutor at Monash University for a period before deciding to pursue journalism as a career. Grattan was recruited by "The Age" newspaper in 1970, and joined the Canberra Press Gallery in 1971. In 1976, she was appointed the Chief Political Correspondent for "The Age", a position she would hold until 1993. After leaving "The Age" in 1993, Grattan was appointed the Editor of "The Canberra Times", becoming the first female editor of a metropolitan daily newspaper in Australia. After two years in this position she was sacked and returned to "The Age", where she became the political editor.