- Start a search window by pressing ⌘f in the finder.
- Now select the small pul-down menu labeled 'kind' and select other...

Doing that, browse trough all the possible options to the 'oolite' part. Check the boxes you like to add in your searches.

The checked boxed now will be part of your default options as shown in the first picture.
- select the kind of search you want. e.g. a ship name or ship role.
- when you add your oxps in the library folder, you must also press the + symbol on the right and add a search category of system files and select to include them, so the library content is also included in searches.
- Do a search on content, not on filename. (but that should be obvious)
And voila:

That will give you all the oxps or saved games were you were looking for.

(Examples were made wilt OSX 10.6)