Hello David,
While there is no way of doing this directly on the Quiz settings page as of Moodle 2.1, within the grader report, there is a work around.
On the Grader report page, select Categories and Items, and add an Outcome Item. On the following page, you can choose to tie the outcome to the quiz.
Essentially, this gives you another thing to mark related to the quiz, so you can use the scale linked to the learning outcome to evaluate how your students have demonstrated their achievement of that outcome in the quiz activity.
It was easier to do this in 1.9, as the Outcomes panel was available on the quiz settings page, allowing you to select multiple outcomes by clicking checkboxes. Having to add them one by one to the grader report is a little tedious - but it will achieve the same purpose.
I've put a tracker item here http://tracker.moodle.org/browse/MDL-31509 on behalf of one of Pukunui's clients. For those who feel this is a useful feature, can I encourage you to comment or vote on the tracker item, or comment here to explain how/why you would use it?
The downside as I see it is that your grader report becomes quite large, the more Learning Outcomes you use, with a column created for each instance. Attaching multiple outcomes to quizzes means instead of them being the friendly little self-marking creatures that make out lives easier, they become something that needs our attention to finalise marking.
Like so many things in Moodle - depends on your purpose as to which way is going to work best for you ;)
Hope this helps!
Lindy