The hosts slumped to 12 for three before Lara and Shivnarine Chanderpaul stopped the rot with a stand of 138 that helped the home side reach 292 for seven at the close.
Lara batted fluently to hit a century for the second consecutive match.
He played his naturally aggressive game and scored his runs off 225 balls with 21 fours and a six, an arcing drive off left-arm spinner Nicky Boje that clattered on to the roof of the Pickwick Pavilion beyond the long-off boundary.
He was eventually dismissed just before the close when he dragged a delivery from fast bowler Andre Nel on to his stumps.
Courtney Browne and Daren Powell were both unbeaten on three when play finished for the day.
Chanderpaul kept the ball on the ground for most of his innings of 53, which ended in the fifth over before tea when he attempted to cut a wide delivery from fast bowler Monde Zondeki and was caught by wicketkeeper Mark Boucher.
The West Indies captain batted for three hours, faced 138 balls and hit six fours.
The tourists had made an excellent start after Chanderpaul had won the toss and chosen to bat.
Nel struck with the fifth ball of the match when left-hander Chris Gayle edged an angled delivery to Boucher for a duck.
Wavell Hinds, on one, pushed forward more decisively at a delivery from Makhaya Ntini five overs later, only to steer it to Graeme Smith at first slip.
Ramnaresh Sarwan drove Ntini sweetly off the back foot through the covers for four before falling for 10 when he cut loosely at a wide delivery from Nel and sent a looping catch to Ashwell Prince at point.
Dwayne Bravo (26) added 115 with Lara for the sixth wicket but South Africa grabbed both of their wickets in quick succession to gain the psychological edge.
By capturing the prized scalp of Lara, Nel finished the day with 3-54.
South Africa left out all-rounder Shaun Pollock who joined the squad in Bridgetown on Monday after missing four Tests and three one-day internationals with an ankle injury.
West Indies included fast bowler Fidel Edwards for the injured Pedro Collins, and all-rounder Ryan Hinds for batsman Donovan Pagon.
South Africa, 1-0 up in the series, made one change, bringing in batsman Boeta Dippenaar for the out-of-form Jacques Rudolph.
Scoreboard
West Indies (1st innings)
W Hinds c Smith b Ntini 1
C Gayle c Boucher b Nel 0
R Sarwan c Prince b Nel 10
B Lara b Nel 176
S Chanderpaul c Boucher b Zondeki 53
R Hinds c Boucher b Kallis 10
D Bravo c Smith b Zondeki 26
C Browne not out 3
D Powell not out 3
Extras (lb-4 nb-5 w-1) 10
Total (for 7 wkts, 89 overs) 292
Fall of wickets: 1-2 2-12 3-12 4-150 5-171 6-286 7-288.
To bat: F Edwards, R King.
Bowling: Nel 20-3-54-3 (nb-1), Ntini 17-2-61-1, Kallis 14-6-37-1 (w-1), Zondeki 14-3-48-2 (nb-4), Smith 8-1-23-0, Boje 16-2-65-0.
South Africa: Graeme Smith, AB de Villiers, Boeta Dippenaar, Jacques Kallis, Herschelle Gibbs, Ashwell Prince, Mark Boucher, Nicky Boje, Makhaya Ntini, Andre Nel, Monde Zondeki.
