Cris Williamson recorded Mary McCaslin's CIRCLE OF FRIENDS on her album "Live in Concert: Circle of Friends" (Olivia Records, 1991)

Mary McCaslin's own recording of CIRCLE OF FRIENDS appeared on her album "Way Out West" (Philo, 1974). It's also on "The Best of Mary McCaslin: Things We Said Today" (Philo, 1992).

Allmusic.com is a great web site for finding out this kind of thing.

First you use their search function to find Mary McCaslin's page:
http://allmusic.com/artist/mary-mccaslin-p19241
Then you click on the "songs" tab, which brings you here:
http://allmusic.com/artist/mary-mccaslin-p19241/songs
The "Highlights" tab will be selected by default; if you click "All Songs" you will see a list of songs that Mary herself recorded, in alphabetical order:
http://allmusic.com/artist/mary-mccaslin-p19241/songs/all-songs
Or, if you click "Songs Composed By" it will show you a list of songs that Mary McCaslin wrote that other people recorded:
http://allmusic.com/artist/mary-mccaslin-p19241/songs/songs-composed-by
You can find more information by clicking on song titles, album titles, performers' names, and so on. Play with it! By clicking on the little speaker symbol, you can hear a sample of about 30 seconds