Filmed on location at genuine convents in London and Ireland, In This House of Brede premiered February 27, 1975, as a GE Theater TV special. ~ Hal Erickson, All Movie Guide
From the Close Up (GE Theater, channels 4 & 10) in the respective issue of TV Guide it says "Most of the interior scenes were filmed at St. Mary's Convent near London and exteriors at Druishane Convent near Killarney, Ireland".