Jarrod Bowen was on hand to pounce within 15 minutes of his full West Ham debut with a lovely run in behind followed by a dinked finish over Alex McCarthy after James Ward-Prowse had given the ball away for Southampton.
With Danny Ings fit only for a spot on the bench, youngster Michael Obafemi stepped up in his place to lift Ward-Prowse's cutback into the goal on the half hour mark.
The Hammers have needed more from record-signing Sebastien Haller this season, and he gave the fans something to cheer about as he beat McCarthy to a ball in the air before squirming the second ball into the net from a tight angle.
It was route one for the third goal as the ball went from one end of the pitch to the other within seconds. Haller headed Lukasz Fabianski’s long kick to Pablo Fornals who sent through Michail Antonio to rifle a shot into the roof of the net and give manager David Moyes a vital triumph.
A Bowen arrow
Handed a first start in the claret and blue, Bowen made his mark in front of his new home fans and staked his claim for regular action as West Ham look to avoid relegation.
Operating initially from the right hand side alongside Haller, Bowen showed a great willingness to run beyond his striker, drifting inside and stretching the Southampton defence with his movement.
That was exactly how he opened the scoring, demonstrating a desire and hunger to get in a goalscoring position and matching his intelligent movement with an equally nifty and high class finish.
A big-money signing on deadline day, Bowen is still equal third in the Championship top scorers list despite having left Hull City over a month ago and he is beginning to prove his quality in the Premier League.
At 23 years of age, a bright future at the top of the English game beckons and Hammers fans will be hoping he can continue this form as they look to stave off relegation.
Errors cost Saints dear
The visitors might well have stayed in the game had they not gifted West Ham two goals in the first half, continuing a worrying trend for Ralph Hasenhuttl’s side.
Ward-Prowse turned the ball over with a poor pass in a bad area for the opening goal, and his teammates failed to react in time as Fornals threaded Bowen through.
The second came from McCarthy as he failed to claim the ball in his area, far too easily beaten in the air by Haller and left forlorn on the grass while the Frenchman turned the ball in the net.
Goalkeeper provides a point of questioning for Hasenhuttl. Angus Gunn began the season in fantastic form but has since played second fiddle to McCarthy, while Fraser Forster has impressed on loan back at former club Celtic.
This was another three points that got away from Southampton after a promising start and is the type of result that needs to be cut out if the club is to progress going forward.
European dreams take a hit
Perhaps a wishful thought, but European football has presented itself as a more than reachable target for Southampton in recent weeks, especially with the possibility of the qualification spots moving down in the table in the aftermath of Manchester City’s European ban.
Should results go against Hasenhuttl’s side, Saints could be eight points adrift of eighth-place come of the end of this weekend’s matches, a margin that with 10 games to go could prove insurmountable.
The fact that Southampton are even remotely in the European conversation after their early season exploits is credit enough, but the fans may have to keep dreaming a little while longer for their team to return to continental football.