During that time, Southampton finished sixth and seventh in successive seasons in the English top flight before Keegan left in August 1982 to join Newcastle.
Magilton will be the Flavio Briatore-led board's fifth manager since they took over in August 2007 (with two caretakers: Mick Harford and Gareth Ainsworth) and QPR's seventh in three-and-a-half years.
Many Arsenal fans were incensed when captain Robin van Persie was sold in August to traditional rivals Manchester United, with the league leaders now 15 points ahead of a team lying seventh in the Premier League after 16 rounds.