The Tampa Bay Rowdies, who never had won a game in Giants Stadium, remained alive in the NASL playoffs there last night by defeatng the New York Cosmos, 3-2, in a shootout, to even their quarterfinal series at one game apiece.

The deciding game is scheduled for Wednesday at Giants Stadium.

With the Rowdies leading the shootout, 3-2, David Mehmet shot the ball to the right of Cosmos' keeper Hubert Birkenmeier to the far corner to give the Rowdies an insurmountable 4-2 advantage.

It gave the Rowdies their third victory in as many shootouts. The Cosmos have lost four of five.

The Cosmos, who trailed 2-1 at halftime, dominated the second half and finally tied the core on a goal by Julio Cesar Romero at 85:06. He left-footed a shot into the far corner of the net on a breakaway pass from Valdislav Bogicevic. But Romero apparently reinjured his left ankle on the play and was replaced by Ricky Davis.

The Rowdies outscored the Cosmos in the first half and would have taken a 2-0 lead into halftime were it not for a controversial goal with 54 seconds to play. Bob Iarusci headed a Romero pass into the outstretched arms of keeper Kevin Keelan, who appeared to drop the ball over the goal line just inside the goal post.