They use to boo Giorgio Chinaglia at Giants Stadium. Not any more. Today the crowd of 42,324 chanted "Geor-gi-o" from beginning to end and the chunky Italian striker responded with three goals that carried the Cosmos into Soccer Bowl '80.

The Los Angeles Aztecs scored first, after less than six minutes, but Chinaglia took care of the rest of the day's goal production and the Cosmos prevailed, 3-1, in the National Conference final. They had captured Wednesday's opener in the Rose Bowl by a 2-1 score.

Leo Van Veen sent the Aztecs in front early an there was momentary panic among Cosmos supporters as Los Angeles kept up the offensive pressure. pThen Chinaglia scored on a header off Julio Romero's corner kick at 12:45 to tie it.

It was still tied with 22 minutes remaining, the Cosmos vainly pleading for penalty kicks when Chinaglia and Franz Beckenbauer were hauled down in the penalty area and the Aztecs coming close as Virginian Gary Etherington sent a hooking shot off the crossbar.

Then Romero, hooted by the fans for his frequent off-target passes, made one that was beyond criticism. He lured two defenders toward him, then pushed the ball through to Chinaglia, who turned and drilled a hard shot over the head of goalie Alfredo Anhielo. The netminder had wandered too far out, to the edge of the box, and the shot curved over his leap and dropped into the net.

For an encore, Chinaglia outfought Aztec defender Wim Suurbier of Angelo DiBernardo's pass on his own side midfield. Racing side by side with Suurbier for 50 yards, Chinaglia suddenly gave his shadow a slight push and fired the ball pass Anhielo.