In 1931 she was elected Abbess of Stanbrook. Dame Laurentia as she became known also served the wider Benedictine community as a member of the commission, set up that same year, with an aim to modernise the various constitutions that governed the conditions of monastic life for women in England.
She was a pioneer in the restoration of the Gregorian chant in England and aleading authority on music and medieval manuscripts. In 1934 her work was recognised by Pius XI who bestowed upon her the Bene Merenti medal for her contribution to Church music.
She died in 1953 having spent seventy of her 87 years within the strictly enclosed monastery.
A stage play based on a book by Hugh Whitemore, The Best of Friends, provides a window on the friendships of Dame Laurentia McLachlan, OSB with Sir Sydney Cockerell and George Bernard Shaw through adaptations from their letters and writings. In a 2006 production at the Hampstead Theatre, Patricia Routledge played the part of Dame Laurentia.