Anyone know what goes into a quest design document for an RPG? I'm going to apply at a company and they want me to send them one but I'm not sure what kind of content it consists of.

Not sure how much it will help, but from Swords & Circuitry page 181. Which he describes as a quest structure.

Notification: The player learns what the situation is or what needs to be done. At this point they are usually also informed what potential benefit may be reaped for completing the task.

Process: The player engages in whatever activities are neccessary to complete the task.

Reward: The player goes to a predetermined place or person in order to receive a reward for their efforts.

*edited for broken link*

Add on top, list the requirement and condition to begin the quest.

I have a funny feeling you will also need a quest flowchart explaining how one quest lead to another. If you are applying to bioware... I'm sure they'll be expecting a lot more.