GORDON Greer's first-half strike sentenced the below-par Baggies to their first defeat in six pre-season games.
Roberto Di Matteo's side never settled into their passing stride and Greer's fine 33rd-minute header had been coming, as the Baggies struggled to deal with balls pumped into their penalty area.
Filipe Teixeira and Swindon old boy Simon Cox both wasted git-edged chances either side of the break, but Danny Wilson's men were not to be denied a deserved victory.
Di Matteo rang seven changes for the County Ground clash as Teixeira was handed his first pre-season start.
Dean Kiely, Gianni Zuiverloon, Abdoulaye Meite, Shelton Martis, Youssouf Mulumbu and Craig Beattie also came in for Scott Carson, Leon Barnett, Jonas Olsson, Marek Cech, Jonathan Greening, Chris Brunt and Luke Moore.
Cox was afforded a warm welcome by the home fans as he made a quick-fire return to the club he left only three weeks ago in a £1.9million Hawthorns switch.
And he almost laid on an Albion goal after just 30 seconds when he dispossessed ex-team-mate Greer and fed Koren.
Unfortunately, the Slovenian's attempted through-ball was slightly over-cooked, allowing Robins keeper David Lucas to smother Beattie's point-blank stab.
The Baggies soon had their own moment of concern when Michael Timlin raced clear down the left and pulled the back for Berlin Ndebe-Nlome, who was denied a clear sight of goal by Zuiverloon's last-ditch challenge.
It had already been an entertaining opening and Albion really should have been one-up in the fifth minute.
Beattie found Teixeira in acres of space inside the box and the Portuguese playmaker looked certain to score as he squared up to Lucas, only to pull his shot wide of the near post.
Back came Swindon and Sean Morrison should have done much better with a free header from Anthony McNamee's corner, with his weak effort easily hacked away by Dwayne Samuels.
The end-to-end action continued in the 20th minute when the unmarked Lecsinel Jean-Francois failed to make the most of a decent heading opportunity from Jonathan Douglas' centre.
Albion broke upfield and Koren was only a whisker away from breaking the deadlock when he drilled Zuiverloon's pull-back inches wide of the far post from just inside the box, with Lucas beaten.
The Baggies almost shot themselves in the foot when Mulumbu was dispossessed deep inside his own half and Billy Paynter curled the loose ball agonisingly wide from 20 yards.
Then, a McNamee corner fell perfectly for Greer whose 12-yard volley was brilliantly palmed away by the alert Kiely.
Albion had struggled to cope with Swindon's aerial prowess all game and it was no real surprise when the hosts snatched a 33rd-minute lead from a corner.
Unmarked skipper Greer ghosted towards the near post and flashed a superb header into the far top corner from McNamee's flag-kick.
A foraging Zuiverloon run down the right-wing almost earned Albion an instant reply. The ball broke for Koren 12 yards out but his goalbound swivel and shot was blocked by Kevin Amankwaah.
At the other end, Greer almost added a second when he was again allowed to attack McNamee's near-post corner. This time, his right-foot volley was gathered by the well-positioned Kiely.
The Albion rearguard continued to look troubled and Swindon would have been celebrating a two-goal cushion on 40 had Alan O'Brien's centre not been a couple of inches too high for Ndebe-Nlome, who couldn't keep his free header below the bar.
Di Matteo rang two changes at half-time, with Barnett and Borja Valero coming on for Samuels and Koren.
Albion started the second period brightly but Beattie failed to make the most of a half-chance when he blazed wide from just inside the box after racing onto Teixeira's exquisite crossfield ball.
But the game soon descended into a scrappy passage of play, which was only briefly broken up in the 57th minute when Morrison headed weakly at Kiely from McNamee's centre.
Albion just couldn't find any rhythm and Di Matteo made two more alterations just past the hour mark, bringing on Cech and Brunt for Mulumbu and Teixeira.
The Baggies finally got another sight of Lucas' goal on 66, but Beattie was just wide with a 20-yard free-kick.
Another lull in the goalmouth action ensued until Town sub Lloyd Macklin flashed a ferocious 20-yard drive just over in the 73rd minute.
Albion were gifted a great chance to level the scores in the 78th minute when Cox seized on Douglas' weak back header .
The former Reading striker looked certain to score on his old stomping ground when he lifted the ball over the advancing Lucas - only for his effort to loop the wrong side of the near post.
Beattie then engineered a shooting chance for himself inside the box from Cech's crossfield ball - but could only shoot straight at Lucas from 15 yards.
The final chance of the game fell to Jon-Paul McGovern who volleyed over from fellow Swindon sub Callum Kennedy's centre.
SWINDON (4-4-2): Lucas; Amankwaah (Cuthbert 86), Greer (C), Morrison, Jean-Francois; O'Brien (Marshall 64), Douglas, Timlin, McNamee (Kennedy 75); Paynter (McGovern 79), Ndebe-Nlome (Macklin 64). Subs not used: Smith, Thompson, Ifil, Easton.
ALBION (4-4-2): Kiely; Zuiverloon, Meite, Martis, Samuels (Barnett HT); Koren (Valero HT), Dorrans, Mulumbu (Cech 62), Teixeira (Brunt 66); Beattie, Cox. Subs not used: Carson (gk), Greening, Olsson, Moore.
GOALS: SWINDON - Greer (33).
BOOKINGS: None.
REFEREE: S Hooper.
ATTENDANCE: 2,482
ALBION STARMAN: Graham Dorrans.
MIDFIELD MUSCLE...Mulumbu battles to keep hold of the ball at the County Ground
