Searching the education databases is a good place to start.

If searching with the phrase “action research” doesn’t get enough results when combined with words targeting the subject, try adding more terms that describe action research.  

Some suggestions:
"action research" OR "problem of practice" OR "practice based" OR “action based” OR "case study" OR "applied research" OR "participatory research" OR "practitioner research" OR "teacher researchers"

Is your research question really complex? Try searching for the most important elements and use the same strategy of using more terms for each of the elements.  For example:

         “action research” OR any of the other terms you decide to use
AND     Reading
AND    learning disab* OR dyslexia

Looking for examples of Problem of Practice dissertations? See the advice on the Library Know How for Education Guide.