Carlos Martins gave Portugal the lead before Postiga grabbed two and Hugo Almeida completed the rout in the final moments...
It was a game that bore no resemblance to the match between the sides in South Africa this summer that ended 1-0 to Spain. Portugal started at lightening quick pace and were close to taking the lead when Nani hit a low shot from the edge of the area that needed to be tipped wide by Iker Casillas, who only just managed to do so.
Spain took a while to find their stride as it was Portugal and in particular Nani who had the forward momentum early on.
However, Spain crept into the game and started to exert their dominance on the Portuguese with Andres Iniesta becoming more and more influential for the visitors.
As Spain upped the tempo of their passing, Portugal were forced back and had to settle for some very effective counterattacking football.
But it was Spain who had the most clear cut chance in the first half as Joan Capdevila strode down the left and following a delicate one-two with Xavi, he delivered an inch perfect cross for an unmarked David Silva, but he could only head wide from six yards. It was an unbelievable miss.
Nani then thought he put the hosts in front when Cristiano Ronaldo lifted a ball over Casillas and just as it was about to cross the line Nani touched the ball over. As he was in an offside position it was ruled out by the assistant referee.
Moments later it was Portugal's turn to squander a gilt-edged chance.
The Manchester United winger was once again involved and striding into the penalty area from the right, he cut a superb ball back into the path of an onrushing Carlos Martins, but he smashed the ball high and wide when it seemed easier to score.
It wasn't long before the Benfica midfielder made up for that error as just before half-time Ronaldo cut in from the left and shot across Casillas only for his Real Madrid team mate to parry into the path of Martins, who made no mistake this time and lashed the ball in from 12 yards out.
The match was to get worse for the world champions as less than five minutes after the restart Portugal went two up. Joao Moutinho burst through a static Spain back line and cut back to Helder Postiga whose cheeky back heel flick delighted the home crowd and stunned the visitors.
After the second went in, both teams made a number of changes which disrupted the flow of the game, something that aided Spain who started to control the encounter.
With the pressure increasing on the Portugal goal, Cesc Fabregas went close with an acrobatic effort not long after a Sergio Ramos free kick was deflected for a corner.
Portugal then scored a third thanks to some wonderful play by Danny on the right, who played in Postiga for his second of the match.
Spain grew frustrated with a number of tasty challenges flying in, but they were unable to make any real headway against an impressive Portuguese team, who made it four and completed a rout in the final seconds of the game thanks to Hugo Almeida.