 He was honorary minister in the McIlwraith-Nelson ministry from May to October 1893, and again Minister for Justice and Attorney-General of Queensland in the succeeding Nelson ministry from October 1893 to October 1894, then postmaster-general until March 1897, and from March 1896 to March 1898 minister for agriculture.He took a particular interest in agriculture, and was largely responsible for the founding of the agricultural college at Gatton and for the state experimental farms.During this busy period of Thynne's life he also represented Queensland at the 1891 federal convention, at the 1894 Colonial Conference held in Ottawa, Ontario, Canada and at the postal conference at Hobart, Tasmania in 1895, and at the Pacific Cable conference in 1895-6.