Local tradition claims that St. Patrick himself founded the monastery here, choosing this spot for its excellent sloping land that leads down to Lough Foyle to the east. The site's significance was further revealed in 2014 when the Bernician Studies Group conducted a magnetometer survey in the surrounding fields, uncovering the outline of the original ecclesiastical enclosure that once defined the boundaries of this Early Christian monastery.

A routine clean-up of the graveyard in 2010 turned into something of an archaeological treasure hunt, bringing to light several previously unrecorded cross-slabs, a quernstone or millstone, and an intriguing architectural fragment from the medieval period. This fragment, now positioned north of the eastern end of the church ruins, offers a tangible link to Cooly Church's medieval past. Carved from brown sandstone, this chamfered jamb-stone once framed a window in the medieval church; its glazing groove and iron bar hole still visible, telling the story of how light once filtered through coloured glass into the sacred space.

Today, visitors to Cooly can trace the layers of religious life that have shaped this corner of Donegal for over a millennium. From the earliest Christian settlers who may have walked with Patrick himself, through medieval builders who crafted elegant windows for their church, to the modern archaeological techniques that continue to reveal the site's hidden depths, Cooly represents the continuous thread of Irish ecclesiastical heritage.