Birthday boy Tevez, 27, two strikes from the penalty spot bookended a beautiful team-goal as the game was put well beyond their visitors. The result saw the Baggies slip to 16th place and just two points away from the relegation spots.
For the hosts, Edin Dzeko paid for his underwhelming start to Premier League life with a spot on the bench. The Bosnian was one of three changes from the side that drew 1-1 at Birmingham City as manager Roberto Mancini brought in Kolo Toure, Pablo Zabaleta and Yaya Toure for the concussed Micah Richards, injured Nigel de Jong and the out of sorts centre forward.
Baggies boss Roberto Di Matteo reacted to the 2-2 stalemate with Wigan Athletic with four changes of his own. Injury meant Gonzalo Jara and Simon Cox were only fit enough to be substitutes, while Marek Cech was ruled out all together.
Steven Reid, Marc-Antoine Fortune and Nicky Shorey filled in, with James Morrison called up to cement the midfield in place of Arsenal loanee Carlos Vela.
The match began in a celebratory- but sombre- tone as City gave 1969 FA Cup final hero Neil Young a minute's applause after he passed away from cancer on Thursday.
The attacker would have been proud in just the fourth minute as Carlos Tevez struck Boaz Myhill's post from 12 yards out. The Argentine latched on to a chipped pass from Aleksandar Kolarov who was deployed in an unfamiliar left-wing role.
Mancini continued to urge his players to push on and in the eighth minute makeshift full-back Reid had to be alert to steal the ball off Yaya Toure's toes inside the box.
The Baggies finally sparked into life after 12 minutes when Joe Hart was called into action twice. The England international pushed a venomous Chris Brunt set-piece away for a corner and then pushed Jonas Olsson's header over the bar from the subsequent corner-kick.
Referee Martin Atkinson then poured water on West Brom's resurgence as he pointed to the spot on 16 minutes after a Reid push on Kolarov. The decision seemed soft but Carlos Tevez showed no mercy and confidently sent Myhill the wrong way despite misses from his previous two penalty-kicks.
If the official was at the centre for the opener there could be no controversy about Tevez's glorious second goal in the 22nd minute. The striker profited from the space created as Vincent Kompany surged forward from centre-back and laid the ball to him on the edge of the area.
An intricate one-two with David Silva - courtesy of the Spaniard's back-heel- followed. In acres of space, Tevez then hurdled Olsson's last-ditch slide tackle and side-footed the ball well beyond Myhill's reach to the delight of the Eastlands crowd.
The Wales international had been unable to get anywhere near Tevez's second but he produced an athletic save on the half-hour mark to deny Kolarov a long-distance double after his strike against Birmingham. The Serb - who benefited from a position pushed up the pitch - unleashed a thunderous shot that was unable to evade Myhill's reach despite its dip and swerve.
Myhill was again tested on 34 minutes as he cleared away Silva's low drive with his legs after the playmaker evaded the sloppy Baggies off-side trap.
The hosts had been at their rampant best in the opening period and Tevez completed his third hat-trick of his City career with another penalty on 39 minutes. There could be no complaints this time about the award as Jerome Thomas clumsily handled Olsson's stretched header to present the Argentine with the perfect opportunity to peg back Manchester United's Dimitar Berbatov in the race to become the division's top scorer.
In a first-half to remember for Tevez, he then went inches away from slotting home a fourth after he again fed off Silva. His cross-shot slid just beyond Myhill's back-stick shortly before Atkinson ended West Brom's first-half agony.
Stung by his charges lacklustre performance, Di Matteo wielded the axe at half-time to replace Thomas with Vela. From his forlorn, hands in coat pocket demenour on the touchline, the Italian saw West Brom finally begin to make inroads into the opposition.
However, it was City who first threatened. Five minutes after the restart the visibly out of sorts Yaya Toure mis-hit a simple pass to Tevez which would have allowed the Argentine a free run at Myhill's goal.
The Baggies continued to get their foot on the ball for the first time as City sat back and absorbed the pressure in a clinical performance worthy of title contenders.
On 62 minutes, the Baggies' possession was nearly rewarded as Youssuf Mulumbu threaded in Fortune but he could only fire into Hart's side-net. Minutes later and Brunt tamely shot wide when in space 25 yards out.
The Ulsterman's travails at Eastlands had given West Brom little chance of recording a result and his poor shot summed up the display.
The match continued in the same fashion as City chose to soak up pressure and strike on the counter. On 78 minutes, Tevez blasted wildly over from 10 yards with the goal at his mercy after Gareth Barry set him up following a poorly cleared corner.
With the crowd's attention now set on events at St. James' Park as title rivals Arsenal steadily threw away a 4-0 lead against Newcastle United, substitute Dzeko dominated the final moments. The Bosnian was a foot away from a low Milner cross on 82 minutes before Steven Reid blocked a goal bound effort from the edge of the box five minutes later.
City, buoyed by a rare appearance from favourite Shaun Wright-Phillips, continued on the front foot until the final whistle was blown. Before the match, Tevez had called for consistency if his club could be considered title challengers, and on this dominant display, he could have had few complaints.
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