The 30-second clip shows the cast pulling together to create a memorial for Cory's character Finn, while a tearful Lea Michele sings the moving Bob Dylan track Make You Feel My Love in the background.
The characters gather around Finn's locker to leave heartfelt notes and gifts in memory of the quarterback.
"I locked [the episode] today. It was incredibly difficult to work on. It was very difficult to shoot," said creator Ryan Murphy.
"I mean, the interesting thing about that show is that those actors and the creators really, really loved Cory," he added. "The episode is called The Quarterback, and you know Cory really was that, to that group of people and to me particularly. There was nobody on that crew that did not like Cory."
"I've never seen a crew that you can't continue shooting because they've left the room sobbing. It was very hard...It was rough. It was very rough. It was very rough with Lea Michele... but I'm very proud of it.
"I think the performances are quite stunning. People still are not over it. It's still very, very difficult."
The episode which airs on 10 October on Fox includes several ex-cast members including Amber Riley who plays Mercedes and Mark Salling who plays Puck.