She was born in Bath and grew up in Barnet, Hertfordshire. When she was 13 it fell to her to cook for her mother and younger brother and sister when her father died and her mother had to return to work as a teacher. After leaving school and taking a cooking course Marguerite was employed as a home economist at the Eastern Electricity Board. She then worked as an actress in repertory theatre for 9 months and for Frigidaire promoting the benefits of the refrigerator as a senior home economist.

During World War II she worked for the Ministry of Food suggesting nourishing and inventive recipes using the rationed food that was available. She broadcast her ideas and advice to the nation on a BBC radio programme called the Kitchen Front. When the war ended she demonstrated kitchen appliances for Harrods.

She was one of the earliest 'celebrity chefs', presenting her first television cookery programme on the BBC in 1947. She has sold 17 million copies of her 170 books, and continues to contribute to tv and radio food programmes to the present day.

Her approach to cookery instruction included teaching essential knowledge and skills needed in the kitchen. Her advice and books were instrumental in improving the quality of British cookery in the post-war years, when rationing meant that more exotic dishes were impossible to prepare.

She was appointed Officer of the Order of the British Empire (OBE) in 1991 for "services to the art of cookery" and Commander of the Order of the British Empire (CBE) in the 2010 Birthday Honours. In 2007, she received the Woman of the Year award, Lifetime Achievement Award.