Goals from Andrew Surman and Grzegorz Rasiak ensured Southampton progressed to the FA Cup fifth round at the expense of League Two's Bury.
The visitors impressed, with Richie Baker hitting the post and Andy Bishop also shooting wide in the first half.
Saints took the lead through Surman's 20-yard effort, which deflected off skipper Paul Scott.
Rasiak sealed the win when he netted from the second rebound after Jim Provett had saved his initial penalty.
Bury - lying 88th in the Football League - were the better side and could have taken the lead in the second minute only for Richie Baker's curling free-kick to hit the foot of the post.
Five minutes later and Baker was allowed to run unopposed through a statuesque Southampton midfield but keeper Kelvin Davis was alert to the danger.
Saints, under the guidance of caretaker managers John Gorman and Jason Dodd following George Burley's departure for Scotland, brought on Inigo Idiakez for defender Andrew Davies at the break.
And the change seemed to pay dividends as Surman forced a first meaningful save from Provett in the 47th minute.
Surman finally broke the deadlock when the England Under-21 midfielder collected the ball 20 yards out, and his low shot deflected off Scott and past the wrong-footed Provett.
Victory was then secured when Scott fouled substitute Stern John in the area and even though Rasiak's initial effort was saved, as was his second, he guided the ball past Provett at his third attempt.
Southampton: Davis, Thomas, Powell (Skacel 64), Davies (Idiakez 46), Vignal, Hammill (John 76), Euell, Wright, Surman, Wright-Phillips, Rasiak.
Subs Not Used: Bialkowski, Saganowski.
Goals: Surman 71, Rasiak 80.
Bury: Provett, Haslam, Futcher, Scott, Woodthorpe, Stephens, Baker, Barry-Murphy (Mangan 81), Buchanan (Dorney 85), Bishop,Adams.
Subs Not Used: Challinor, Hurst, Anane.
Att: 25,449
Ref: Stuart Attwell (Warwickshire).
BBC Sport Player rater man of the match: Southampton's Adam Hamill 8.33
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