JAMES Morrison's brilliant first goal in 15 months set up Albion's eighth successive home league win - and propelled them 12 points clear in the second automatic promotion berth.
The former Middlesbrough midfielder, who only returned from a long-term injury lay-off six weeks ago, became the Baggies' 21st different scorer this term with a 25-yard half-volley in the 38th minute.
Robert Koren ensured play-off hopefuls Leicester were heading for a fourth consecutive defeat with a fine double - his seventh and eighth goals of the season.
The Slovenia skipper blasted home in first-half stoppage time before sealing the points with a coolly-taken second five minutes from time.
This was a thoroughly professional performance by the hosts whose extra goal power saw them through this bruising encounter.
Albion's sixth 'double' of the season, after winning 2-1 at the Walkers Stadium in November, made it a perfect day for Roberto Di Matteo in the 100th game of his short managerial career.
Di Matteo made four changes - two enforced - as fit-again trio Koren, Chris Brunt and Marek Cech, plus Ishmael Miller, came in for the injured Jerome Thomas, Chris Wood, Joe Mattock and former loan signing Ben Watson, who was called back yesterday by parent club Wigan.
The Baggies were also buoyed by the return to the bench of Roman Bednar after a four-game thigh-injury absence while Andy Slory returned to the 18 for the first time in seven matches.
Former Baggies assistant boss Nigel Pearson, taking charge of his 100th game as Leicester manager, also made four changes, with Matt Oakley, Steve Howard, Bruno Berner and ex-Baggie Lloyd Dyer coming for Paul Gallagher, Jay Spearing, Nolberto Solano and Danny N'Guessan.
Dyer was given a warm welcome by the home hordes on his return to his old stomping ground - and then set about upsetting them by making a lively start to the game.
After Berner had beaten Scott Carson to a Martin Waghorn free-kick and headed well over, Dyer cut inside Steven Reid before blasting the ball just wide from 15 yards.
Dyer then had the Baggies rearguard back-pedalling with a forceful dart into the box and Carson had to rush off his line to nick the ball off the winger's toes before Cech cleared.
Albion saw plenty of the ball during the opening stages but did not threaten until the 17th minute, when only the woodwork denied them the opening goal.
Jonas Olsson towered in the box to beat City keeper Chris Weale to Brunt's dangerous free-kick and the Swede saw his downward header clip the outside of the post and bounce wide.
That close shave sparked a mini-spell of Baggies pressure and the unsighted Weale did brilliantly to push away Miller's fierce 20-yard drive before Berner cleared.
Leicester were back on the attack on 20 when Howard raced onto Richie Wellens' slide-rule pass and took the ball away from Carson before crossing. Thankfully for Albion, Cech was well-positioned to head the danger away from the empty net under pressure from Waghorn.
Moments later, the Foxes almost shot themselves in the foot when Brunt read Robbie Neilson's attempted back-header to Weale, but the keeper just beat the former Sheffield Wednesday midfielder's outstretched boot to the ball before gathering at the second attempt.
The game then descended into a war of attrition, with defences very much on top - until Morrison broke the deadlock on 38 with a stunning strike.
Jack Hobbs could only head Brunt's left-wing centre to the edge of the box and after Graham Dorrans had nudged the ball into Morrison's path, the Scotland international smashed it home off the left-hand post with a 25-yard half-volley.
Albion oozed confidence after the breakthrough but they had a little scare four minutes before the break when Dyer cut inside Olsson before firing into the side-netting from 15 yards.
However, Albion took the game by the scruff of the neck by surging two-up in the first minute of first-half stoppage time.
Hobbs' attempted headed clearance from Brunt's free-kick ricocheted off team-mate Neilson before falling perfectly for Koren, who drilled past Weale from 12 yards.
Albion suffered a setback during the half-time interval, with Reid unable to continue. Gabriel Tamas shuffled across to right-back while sub Abdoulaye Meite slotted in at centre-half.
The Baggies' new-look defence had a huge let off within three minutes of the restart when Howard shrugged off Olsson to control Neilson's huge throw-in into the box before firing wastefully wide from 15 yards.
That lucky escape sparked Albion back into life and Weale did well to push away Tamas' stinging 18-yard drive after Morrison had spearheaded a swift counter-attack.
Leicester took full advantage of a poor Miller lay-off when Andy King found Howard in the box with an inch-perfect lofted pass.
The former Derby forward turned the ball inside Meite before chipping harmlessly wide of the on-rushing Carson's goal.
Miller's final contribution, before he was replaced by Bednar in the 57th minute, was to fire wildly over from an acute angle following a Berner error.
Back came Leicester but King failed to trouble Carson's goal with a 20-yard curler after dispossessing the otherwise impressive Youssouf Mulumbu.
Albion threatened twice in quick succession when Berner had to be in the right place at the right time to prevent Koren getting on the end of Bednar's cross. Seconds later, Morrison ran at the Leicester defence before firing wide from 20 yards.
Leicester certainly weren't giving up without a fight but sub James Vaughan could only loop a harmless header onto the roof of Carson's net from Neilson's cross.
Michael Morrison should have done much better ten minutes from time when he volleyed high and wide from the edge of the box after the spinning ball had evaded Meite.
There was huge controversy at the other end a minute later when referee Darren Deadman waved away strong Albion penalty appeals despite Berner appearing to handle Koren's right-wing cross.
But Albion put the game to bed five minutes from time when ice-cool Koren raced onto Morrison's defence-splitting pass before rounding Weale and slotting into the empty net.
The Baggies' third clean sheet in five games was secured when Carson denied Vaughan with a low save before Meite brilliantly blocked the on-loan Everton striker's goalbound effort from the rebound.
Albion almost made it four in the first minute of stoppage time when Dorrans powered into the box and saw his fierce effort kept out by Weale.
ALBION (4-5-1): Carson; Reid (Meite HT), Tamas, Olsson (Mattock 78), Cech; Koren, J Morrison, Mulumbu, Dorrans, Brunt; Miller (Bednar 57). Subs not used: Kiely (gk), Cox, Barnes, Slory.
LEICESTER (4-4-2): Weale; Neilson, Hobbs, M Morrison, Berner; King, Oakley (Adams 61), Wellens, Dyer (Vaughan 53); Waghorn (Gallagher HT), Howard. Subs not used: Logan (gk), Brown, Kermorgant, Spearing.
GOALS: ALBION - J Morrison (38), Koren (45+1, 85).
BOOKINGS: ALBION - Carson (time-wasting 65), Tamas (foul 70). LEICESTER - Waghorn (foul 37).
REFEREE: D Deadman (Cambridgeshire).
ALBION STARMAN: Marek Cech.