Cowan's mother wanted him to go into banking, but Cowan deliberately failed his math exam in order to avoid this.[3] He then worked in a record shop owned by EMI, eventually becoming marketing manager of the holding company in Ireland.[3] While there, he managed Christy Dignam and the drag act Mr Pussy, and first saw Brendan O'Carroll in performance.[4] After being made redundant in 1992, he was asked to book an act for a venue that would bring in similar crowds to those that had accompanied Mr Pussy and Dignam; and suggested O'Carroll.[4] As a result of this, he became O'Carroll's publicist, and has worked alongside him well into the 2010s.[4] Soon afterwards, O'Carroll developed the Mrs Brown routine, creating the character of Rory Brown specifically for Cowan,[1] although at first, Cowan did not take on the role as he was simply "the logistics man" who organised shows and bookings.[3] The character of Rory Brown originally appeared in the radio slots, and was originally played on stage by another actor who resigned at short notice.[3][5] As a result, Cowan, despite never having acted in front of an audience before, was asked to take on the role by O'Carroll, and his camp performance quickly became the definitive portrayal.[3][5] In 2016, alongside actress Deirdre O'Kane, Cowan was signed up to the Irish version of Gogglebox, screened by TV3.[4]
On 16 June 2017, Cowan gave O'Carroll his resignation notice,[6] and the following month announced he had quit Mrs Brown's Boys.[7] He described his parting from the company as "amicable" and completed a stage tour of the show, but did not appear in the 2017 Christmas special.[8]
In 2019, Cowan joined the RTÉ soap drama Fair City.
On 7 December 2023, it was announced that Cowan would be a contestant on the seventh series of the Irish version of the competition series, Dancing with the Stars.[9] Cowan and his partner Jillian Bromwich were eliminated first.