Tolmie was elected leader of the British Columbia Conservative Party in 1926 but continued to sit as a Member of Parliament until the 1928 provincial election, in which he ran and was elected MLA for Saanich. The Conservatives were victorious that year, taking 32 of the legislature's 48 seats, including every seat in Vancouver and Victoria. Tolmie thus became Premier of the province, also serving as Minister of Railways.