4MacDonogh, Steve. The Dingle Peninsula. Dingle, Co. Kerry, Ireland: Brandon, 2000. 175-77.
While the cross-slab beside Gallarus is common to Christian settlements from the seventh and eighth centuries, the oratory was likely built atop an earlier structure at this site. Its refined construction, principally its east window with the rounded arch, suggest a later date.
H.G. Leask in 1955 observed traces of "very fine lime mortar" used to fill the internal joints and provide pointing for the stones of the interior. (Leask, Harold G. Irish Churches and Monastic Buildings. Dundalk, Ireland: Dundalgan, 1955. 41.)