punctuation - Can 'or' have a comma before it if it starts a dependent clause?

For example, is

All I had to do was step out of my comfort zone, or in this case, be pushed out of it.

or

All I had to do was step out of my comfort zone or in this case, be pushed out of it.

preferable? I think I know which one to use, but I would like to know why I would use it.