As early as 1397 we have the record of Fr O Molgain as parish priest here. Also in the 14th century one Magrocachan (McGrogan) is listed as “Rector of Tulach McInagh”. Hugh O Caoilte (Kielt) is another Pastor of the same period. Bishop Redmond O’Gallagher (martyred 8th March, 1601) made the parish his place of refuge and issued a dispensation from here to the Bishop of Down & Connor, Dr Cornelius O’Devany. Cornelius O’Devany, a Franciscan, was martyred in Dublin in 1610 along with Fr Patrick O’Loughran, a priest from Armagh. The Dispensation issued to him from Tamlaght O’Crilly was used as evidence against him at his trial in Dublin. Both of these martyrs for the faith were beatified along with other Irish Martyrs in 1992.
At the end of the 16th century Tamlaght O’Crilly, Drumagarner, Kilrea and Desertoghill were still separate parishes, but at the beginning of the 17th century (in the year 1610) they were all amalgamated to form the Parish of Tamlaght O’Crilly. In 1631 Vicar O’Cully (recte: Patrick O’Crilly) is named as Rector of Tamlaght O’Crilly.
From 1662 to 1712 Fr Henry O’Crilly was “Pastor of Tamlacht O’Crilly, Kilrea and Desertoghill”. He lived in the townland of Drumlane and rode around the parish on horseback carrying his silver chalice which was in three sections which could be screwed apart for convenience. This chalice is still preserved in the neighbouring parish of Kilrea to where it was transferred from the Diocesan Museum in Derry. In the Registration of 1704 we find Fr Henry O’Crilly resident at Tamlaght O’Crilly along with his nephew, Fr Henry O’Crilly, Junior, who is registered as in charge of the Grange of Agivey. He later became P.P of Moville and his grave is in the ancient graveyard of Cooley near Moville. At the same time a Dominican Friar, Dominic McGowan, was resident with Mr Stafford in Portglenone. Another friar, Patrick O’Hegarty also assisted Fr Henry O’Crilly in the parish at that time.
Fr Aindreas O’Brolchain, a native of Maghera, was Pastor of Tamlaght O’Crilly and Desertoghill in 1766. He lived at Moneysallin where he had a Mass-house. He had another Mass-house at Timaconway. He was know as “An Brathair Ban”.
Fr O’Regan (1770 – 1802) built the original church at Greenlough in the year 1793 on land held by the McErlean and McLaughlin familie (he had previously built the church at Drumnagarner in 1778). The church at Greenlough was thatched and had a clay floor. After Fr O’Regan came Fr John Diamond as Pastor of Tamlaght O’Crilly and Drumagarner.
Later, in 1825, the church was remodelled and slated by Dr John McRory (or Rodgers as he is called in his memorial tablet in Greenlough chapel) who was the last Parish Priest of the united parishes of Tamlaght O’Crilly, Desertoghill and Kilrea. A suspended canopy hung over the altar which was on a raised predella on the south wall of the church (on the side of the church away from the road). Around the altar were three galleries, one at each gable and one in the centre lit by single windows in the gable walls. There were no seats at that time, except for the choir; the congregation stood around the altar on a floor of beaten clay covered with rushes. Dr McRory also extended Greenlough graveyard. Dr McRory had two Curates, Fr Samuel Auterson and Fr John McLaughlin. On Dr McRory’s death in 1838, Fr Auterson was made Parish Priest of the separate parish of Kilrea and Desertoghill and he built the new church at Drumnagarner to replace the old thatched one built by Fr O’Regan.
At the same time (1841) Fr McLaughlin who had become the first P.P of the separate parish of Greenlough re-built the Church at Greenlough and it was in this year that the Church was dedicated to Mary, the Mother of God. Fr McLaughlin transferred to Glendermott parish and ultimately to Ballerin. He was succeeded as pastor of Greenlough by Fr Patrick O’Hassan in 1847. Fr Hassan, a native of Glen, Maghera, was ordained in 1831. He served as curate in Coleraine, Banagher, Faughanvale, Maghera, Clonmany and for a short time is Derry before coming to Greenlough in 1847. He was pastor here for 11 years before transferring to Maghera where he was P.P and Vicar General of the Diocese. He died in 1886.
Fr James McNamee was appointed Pastor here in 1857. He died in 1863 on 28th July aged 65 and is buried at Greenlough. Fr Tom Dempsey was the next parish priest. He built the old Parochial House (now the residence of William John & Betty O’Donnell and family) and he died at Greenlough in 1870. Fr Francis Boyle was his curate for three years and then Fr Anthony Doherty was curate until Fr Dempsey’s death.
Fr George McDonagh or Donaghey succeeded Fr Dempsey in 1870. He was a native of the Foreglen in County Derry. He died in 1905 and there is a memorial tablet to him on the wall of Greenlough Church. His curate was Fr John McNamee. A note in the Baptismal Register in Greenlough under the date 22nd April 1878 reads: “Fr John McNamee comes as Curate 22-04-1878”. Fr McNamee was curate here until 1892 when Fr Charles McGill came as Curate until 1895. Other curates here at this period were, Fr Michael O’Mullan (1895-97); Fr John O’ Callaghan (1897-98); Fr Charles H. Kerlin (1898-1901); Fr Patrick O’Gormley (1905).
Fr Thomas Maguire came as P.P in 1905. He died here on 14th August 1925, aged 70 years. He was responsible for changing the interior design of St Mary’s Church at Greenlough. He changed the altar from the South Wall to the East Gable, installed two side altars of The Blessed Virgin and The Sacred Heart and provided the beautiful carved wooden communion rail, tiled the Sanctuary and constructed the new gallery at the West end.
Fr Charles H. Kerlin, a native of Glenullin, who had been curate here from 1898 in 1904 in the time of Fr McDonagh, was appointed P.P of Tamlaght O’Crilly/Greenlough in 1925. He was here for 10 years before being transferred to the pastoral charge of the parish of Leckpatrick, Strabane, Co. Tyrone. During his time here, he strengthened the walls of St Mary’s Church at Greenlough and enhanced its external appearance by the addition of massive buttresses to the side walls. On Christmas Day 1925 Greenlough Church was first lit by electric light.
Fr Kerlin was very interested in the temporal welfare of the people as well as their spiritual welfare and encouraged local businesses such as the establishment of Clady shirt factory by Teady McErlean.
In 1935, Fr George Ryan came as pastor and he died on 5th January 1941. During his pastorate yet another renovation of the church was carried out and the beautiful stained glass windows were installed. After him came Fr Paul McKenna who died in 1944. One of Fr McKenna’s possessions was a penal crucifix which he bequeathed to his sister. His sister later presented the crucifix, known as “the Greenlough Crucifix” to Fr Martin Rooney who had been Curate here with Fr Paul. Fr Rooney kept the Crucifix carefully and shortly before his death, providentially transferred the sacred object to Greenlough Parish where it is now kept. During Fr Paul McKenna’s brief pastorate, the parish celebrated the Centenary of the Dedication of St Mary’s Church at Greenlough on Sunday, 14th September 1941 – Feast of the Exaltation of the Holy Cross. There was Pontifical High Mass in the morning and in the evening Benediction and a lecture on the history of the Parish by the learned Fr Walter Hegarty. This lecture was published in the Coleraine Constitution newspaper on 20th September 1941. Fr McKenna was P.P here at the time of the murder of Patrick O’Kane, proprietor of The Waterwall. This tragedy happened on Tuesday 1st December, 1942 but the body was not discovered in the Public House until the following Thursday night, 3rd December. Fr McKenna died a year later on 12th December, 1943 and is buried at Greenlough.
The next parish priest was Fr Archibald McMaster, a native of Maghera who later transferred to the pastorate of Donagheady, Co. Tyrone in 1953. His successor was Fr Thomas Hegarty who was parish priest for thirty years until September 1983 when he resigned his parish in favour of Fr Art O’Reilly, the present parish priest. Fr Hegarty built the new Greenlough Primary School at Moneystaghan (opened September, 1962) and St Mary’s Secondary School at Clady (opened 1962) and also the modern church of St Oliver Plunkett at Clady (Dedicated 8th December, 1980).