Born in Glasgow as Anne Catherine Long, she was educated at the city's Our Lady and St Francis Secondary School (became part of St Mungo's Academy in 1988) on Charlotte Street and the University of Glasgow where she was awarded a MA in politics with history. She went on to study for teacher training at the Notre Dame College of Education (merged with Craiglockhart College in 1981 to become the St Andrew's College of Education, then became part of the Faculty of Education of the University of Glasgow in 1999) in Bearsden, gaining a Diploma in Secondary Education.
She worked in the University Court of the University of Glasgow as both a registrar and a secretary from 1971 to 1974. In 1983, she joined Community Service Volunteers (CSV), initially as a teacher, then as a fieldworker. She left the organisation in 1993 as its national officer. Upon leaving CSV, she became the Deputy Director of the Scottish Council for Voluntary Organisations, where she remained until her election to the UK Parliament in 1997.
She was the parliamentary election agent for Norman Hogg at the 1979 general election at Dunbartonshire East, when he ousted the Scottish National Party's MP Margaret Bain (later Ewing). She remained as Hogg's election agent for the 1983, 1987 and 1992 elections in his new Cumbernauld and Kilsyth constituency. She was elected a councillor on Strathclyde Regional Council in 1980 and served for two years. She was a member of the Scottish Labour Party Executive from 1984 until 1997 and Chair of the Scottish Labour Party from 1992 to 1993. From 1987 until 1991, she was a member of the national executive of the GMB Union.
McGuire was selected to stand for election for Labour through an all-women shortlist. She was elected to the House of Commons at the 1997 general election when she ousted the then Secretary of State for Scotland Michael Forsyth by 6,411 votes. In the same year as her first election, she was rewarded by becoming the Parliamentary Private Secretary to Secretary of State for Scotland Donald Dewar. A year later, she was appointed an Assistant Whip's office, becoming a Lord Commissioner to the Treasury in 2001. She became a Parliamentary Under-Secretary of State for Scotlandin 2002, moving sideways to the Department for Constitutional Affairs in 2003. She served in the Department for Work and Pensions with responsibility for disabilities from 2005 to 2008. In October 2008, she stood down from the government and it was announced she would be appointed to the Privy Council.
On 10 October 2010, McGuire was appointed Parliamentary Private Secretary to Leader of the Opposition Ed Miliband along with Chuka Umunna. She also currently serves as a member of the Public Accounts Committee and as co-chair of the All-party group on Disability.
She has been married to her husband, Len, since 12 February 1972 and they have a son and a daughter and live in Cumbernauld. She is a keen linguist and speaks French and Gaelic. She enjoys Ceilidh dancing and is honorary vice-president of Glasgow University Shinty Club.