McGowan had just returned from playing for Australia at the Under-20 World Cup in Egypt.
He told Hearts' website: "I need to be playing regular games. Hopefully being at Ayr will help my game and, in turn, help Ayr climb the table."
McGowan headed home a Ryan Borris cross with 17 minutes remaining as Ayr came from two goals behind to secure a draw that prevented Dundee taking over at the top of Division One.
"I am due to come back to Hearts in January, when I hope to stake a claim for first-team involvement again," he added.