McGrath was first elected to the Down District Council in 2005 as a councillor for the SDLP. He served as both chair and vice-chair, becoming the youngest ever chair of the local council. In 2014 he was elected to the newly formed Newry, Mourne & Down District Council.[1]
He entered Assembly politics when he contested the 2016 Northern Ireland Assembly election, being elected with 5,110 first-preference votes alongside fellow SDLP candidate Sinéad Bradley. The third and incumbent SDLP candidate, Seán Rogers, was not elected and so lost his seat. He was re-elected in the 2017 snap NI Assembly election. During his time in the Assembly, McGrath served as a member of the Education Committee, Business Committee and Procedures Committee.[2]
McGrath has highlighted rural issues, accessibility to local services such as the Downe Hospital and youth issues as his main priorities. He has criticised the eleven-plus transfer system, arguing that a level playing field is required and condemning the branding of 11-year-old children as "failures" if they fail to achieve high marks. He supports his party position that academic selection "brands a large portion of children as failures and puts an inordinate amount of pressure on them". He has however argued that the debate is about academic selection rather than a disapproval of Grammar schools.[3]
He has also served as chairman and Health Spokesperson for the SDLP.[1]
