Morrell was a member of the team that met SDLP and Alliance for talks that led to the formation of the NI Executive, and he was at the Sunningdale Conference where he negotiated the Council of Ireland with Garret FitzGerald.
He introduced the Shannon-Erne Waterway as a cross-border initiative, giving it further encouragement when on the NI Water Council.
Faulkner appointed Morrell as Minister of Agriculture when the Northern Ireland Executive was created.
After Sunningdale when Faulkner resigned after losing a vote on the Agreement in the Unionist Council, and Morrell was expelled from the UUP by the North Londonderry Constituency Association, he joined Faulkner's new Unionist Party of Northern Ireland, becoming deputy leader of the party.
However, Morrell lost his seat in Londonderry in the 1975 elections to the Northern Ireland Constitutional Convention.