McCall replaces Andrew Harrison who announced his departure in December amid reports of a clash over expansion strategy with the founder of the low-cost airline, Stelios Haji-Iannou.
McCall has been with Guardian Media Group for 24 years and group chief executive since 2006. She is said to have been one of the driving forces behind the success of the Guardian’s website, guardian.co.uk, which has about 37 million unique users worldwide.
However, the success of the Guardian’s online offering did not boost profits last year. GMG made a loss of £89.8m in the 12 months to March 2009, from a £306.4m profit a year earlier, and reported turnover dropped to £405m, down from £501m in its previous financial year.
Harrison is understood to have clashed with Sir Stelios over easyJet’s plans to expand and buy new planes during a period of global economic upheaval.
He is to join Premier Inn and Costa Coffee owner Whitbread as chief executive in June.