MASTER marksman Kevin Phillips made it 21 goals in just 20 appearances with a sublime double as the table-topping Baggies signed off 2007 in style in front of a sell-out home crowd.
And the 34-year-old striker would have been celebrating a hat-tick against ten-man Scunthorpe had former Baggie Joe Murphy not saved his 59th-minute penalty.
Phillips' 14th of the season broke the deadlock in the 35th minute - sparking a crazy 12-minute spell.
Iron boss Nigel Adkins was sent to the stands after protesting the opener was offside before United defender Marcus Williams was red-carded two minutes before the break for a professional foul.
There was still time for Robert Koren to fire the Baggies 2-0 ahead deep into stoppage time - his seventh of the season - and Phillips made the points safe with a sublime second in the 52nd minute.
Zoltan Gera ensured Albion scored four times for the third successive home game when he blasted home an unstoppable volley in the 78th minute - his fourth in five matches.
And sub Craig Beattie put the icing on the cake of a festive goals feast with an 81st-minute cracker.
Scunthorpe headed into this first-ever Hawthorns league meeting between the two clubs buoyed by their first win in 12 on Boxing Day, which lifted Adkins' men out of the drop-zone.
Albion were bidding to retain top spot for the first time this term after leapfrogging previous leaders Watford on goal difference thanks to Wednesday's 4-1 demolition of promotion-rivals Bristol City.
Mowbray named an unchanged starting XI. Returning duo Chris Brunt (hamstring) and Filipe Teixeira (illness) replaced keeper Luke Steele and Leon Barnett on the bench.
Scunthorpe made three changes as Kelly Youga, Cleveland Taylor and Jonathon Forte replaced the suspended Cliff Byrne and benched duo Paul Hayes and Kevan Hurst.
Albion put the Iron straight onto the back foot and Youga, back from a four-match ban for successive red cards, had to make two frantic far-post clearances in the opening minutes.
United only stayed level in the eighth minute when left-back Williams hacked Phillips' downward header off the line from Jonathan Greening's corner.
Moments later, it took another vital interception from Scunthorpe skipper Andy Crosby to deny Roman Bednar a clear effort on goal after the Czech international had controlled James Morrison's diagonal ball.
Scunthorpe made life tough for the Baggies by packing men behind the ball and squeezing the space outside their penalty area.
But the visitors were grateful to keeper Murphy, who was given a warm welcome by the home hordes, in the 20th minute when he blocked Bostjan Cesar's goalbound header from Greening's flag-kick.
Seconds later, Gera flashed a header over from another Greening set-piece.
On a rare foray into the Albion half, Scunthorpe gave the hosts cause for concern when Jack Cork was only inches away from connecting with Forte's dangerous centre at the far post.
At the other end, Morrison did brilliantly to dispossess Youga and beat a couple of challenges but his finish failed to match his approach work as he blasted over from 20 yards.
But Albion had a big let-off in the 32nd minute when dangerman Martin Paterson ghosted onto Youga's excellent diagonal pass but failed to make contact with just Dean Kiely to beat.
However, just three minutes later, the Baggies broke the deadlock.
Phillips beat the offside trap to race onto Morrison's exquisite diagonal pass before emphatically beating Murphy with a right-foot volley from 18 yards which looped into the top left-hand corner.
United boss Adkins was so incensed by the referee's assistant's decision to flag Phillips onside that he was sent to the stands for protesting too vociferously.
And the Iron were a man down on the field as well eight minutes later when Williams was red-carded for pulling Gera's shirt as he raced onto Pele's ball over the top.
Although Williams was the last man, the decision seemed harsh as Gera was by no mean's certain to latch onto the pass.
Things got even worse for the Iron in the second minute of stoppage time when Koren made it 2-0 with his second goal in as many games.
Gera slotted Carl Hoefkens through on the right-hand side of the box and he crossed for Koren who smashed the ball home at the second attempt after seeing his first shot blocked by Ian Baraclough.
Mowbray made a change at the break, replacing Bednar with Ishmael Miller.
And the nine-goal striker was soon in the thick of it.
Miller turned Baraclough on the edge of the box before seeing a 20-yard grass-cutter well saved by Murphy.
But the United keeper was powerless to stop Phillips making it 3-0 in the 52nd minute.
Murphy initially though he'd saved United's bacon when he raced off his line to deny Morrison, who had been played in by Phillips.
But the ball spun to the edge of the area where the lurking Phillips audaciously chipped the ball over the Scunthorpe defence and into the empty net. Simply sublime.
Albion were now turning the screw and Murphy again showed a safe pair of hands to hold onto Miller's stinging 15-yard drive.
Miller and Murphy appeared to be locked in a personal duel and the former will feel he should have done better than plant a free header straight at the Iron keeper after a terrific run and cross by Phillips.
Miller won a 59th-minute penalty when he raced onto Phillips' throughball, rounded Murphy and was upended by Youga.
But Phillips was denied a hat-trick when Murphy dived low to his left to palm away his right-footed spot-kick.
The ex-England striker was subbed three minutes later, to a standing ovation, and was replaced by Beattie.
However, it took a stunning 64th-minute double save by Kiely to preserve the three-goal cushion.
The Baggies No.1 brilliantly kept out Ian Morris' header from Cleveland Taylor's set-piece before springing back onto his feet to tip over Taylor's follow-up drive.
Miller was again denied by Murphy before Forte spurned a glorious chance at the other end when he placed the ball wide of the left-hand post after being put clean through.
Miller yet again had his head in his hands after his powerful run into the box and toe-poke was thwarted by Murphy's near-post block.
But the ex-Tranmere keeper was absolutely helpless in the 78th minute when Gera chested the ball down on the left-hand angle of the penalty area before blasting an unstoppable volley inside the far top corner.
Just three minutes later, sub Beattie matched Gera's wonder strike by controlling Greening's pass, skipping inside Taylor and curling the ball into the same part of the net from the same spot.
The five-goal show wrapped up Albion's first double of the season on the back of September's 3-2 win at Glanford Park.
ALBION (4-4-2): Kiely; Hoefkens, Pele, Cesar, Robinson; Gera, Koren (Brunt 77), Greening, Morrison; Phillips (Beattie 62), Bednar (Miller 45). Subs not used: Teixeira, Albrechtsen.
SCUNTHORPE (4-4-2): Murphy; Youga, Crosby, Baraclough, Williams; Cork, Goodwin (Hayes 87), Taylor, Morris; Forte (Winn 87), Paterson (Ameobi 59). Subs not used: Lillis (gk), Hurst.
GOALS: ALBION - Phillips (35 & 52), Koren (45+2), Gera (78), Beattie (81).
BOOKING: SCUNTHORPE - Goodwin (foul 86).
SENDING-OFF: SCUNTHORPE - Williams (professional foul 43).
REFEREE: N Swarbrick (Lancashire).
ATTENDANCE: 25,238.
ALBION STARMAN: Kevin Phillips.
PIC: SUPER KEV...Phillips celebrates his first goal
