Albion, who needed a win to be sure of getting into the play-offs, were home and dry by half-time after scoring four times in the first 40 minutes.
Nathan Ellington set-up Phillips' 21st minute opener and then got on the scoresheet himself to double the lead four minutes later.
Ellington grabbed his second from the penalty spot in the 36th minute before Robert Koren scored his first goal for the club.
Phillips helped himself to a second in the 54th minute before completing a top-class hat-trick after 71 minutes.
To rub salt into Barnsley's wounds, substitute Zoltan Gera rolled home the seventh four minutes later.
Fortunately for Barnsley, they had secured their Championship status for another season before they arrived at The Hawthorns.
Simon Davey's side simply had no answer to rampant Albion, although they did threaten briefly when Dean Kiely saved Sam Togwell's header and Daniel Nardiello was unlucky to see his shot deflected over the bar by Sam Sodje.
But Albion, who had lost four of their last five home games, made their early pressure pay off when Paul McShane whipped in a right-wing cross that Ellington turned goalwards.
Bobby Hassell tried to clear the ball but only managed to deflect it into the path of Phillips who made no mistake from six yards.
Ellington struck for the first time when rookie Barnsley defender Luke Potter - who was making his first start - made the kind of mistake he will not want to remember when he hauled down Koren.
Referee Lee Probert had no hesitation in pointing to the spot and Ellington calmly rolled his penalty beyond David Lucas.
Ellington put the result beyond doubt when he latched on to a long clearance and beat Lucas with a well placed left-foot drive.
Albion's domination was further emphasised five minutes before half-time following a well placed left-wing centre from Jonathan Greening.
Koren cheekily back-heeled the ball past Lucas from just six yards.
The Slovenian international then rattled the bar in the 52nd minute before Ellington turned provider again.
He rolled the ball across the face of the area to Phillips, who showed his accuracy from distance with a 20-yard drive that whistled past Lucas.
Phillips then took his tally for the season to 19 by completing his hat-trick when he steered home a left-wing cross from substitute Gera.
Having set-up Phillips, Gera wanted to get in on the act himself and he made no mistake from 12 yards when he was picked out by Sherjill MacDonald's cross.