If you don't like Graph objects, you can always use FQL
fql?q=SELECT uid, page_id, type FROM page_admin WHERE page_id = {pageId}
returns this:
{ "data": [ { "uid": "6905135096", "page_id": "{pageId}", "type": "ATHLETE" }, { "uid": "14408356540", "page_id": "{pageId}", "type": "ATHLETE" }, { "uid": "51936644133", "page_id": "{pageId}", "type": "ATHLETE" }, { "uid": "7230226073", "page_id": "{pageId}", "type": "ATHLETE" } ] }
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