The futures of both managers were subject to intense speculation in the build-up to a Loftus Road encounter contested by the sides bottom and second-bottom of the standings.
Southampton were quicker to settle and captain Adam Lallana came close in the seventh minute, firing just over after a neat one-two with Gaston Ramirez.
Adel Taarabt – so often a threat for QPR – highlighted the Saints' defensive fragility by breaking through in between Nathaniel Clyne and Jose Fonte, before forcing Paulo Gazzaniga into a quick reaction save.
QPR and Southampton had conceded 49 league goals between them prior to the game and the hosts' defence was breached 23 minutes in as Rickie Lambert bundled home his fifth of the season.
The Rs found themselves further behind at the end of the first half as man-of-the-match Jason Puncheon returned to haunt the club he spent a loan spell with last season, striking home from the edge of the box.
Boos rang loudly around Loftus Road at the half-time whistle but the hosts came out rejuvenated for the second period, with Junior Hoilett clawing one back four minutes in.
That, though, was to be as good as it got for QPR as Southampton wrapped up victory when Anton Ferdinand deflected home Morgan Schneiderlin's late cross.