He was a minister (1952–56) in U. N. Dhebar ministry when 'United State of Kathiawar' was formed.
in 1957 when he won Lok Sabha seat from Surendra Nagar.
In a very closely contested Loksabha election of Rajkot constituency in 1971, Ghanshyam Oza defeated Minoo Masani of the (Swatantra party) and became a minister in the cabinet of PM Indira Gandhi.
[7] Oza opposed the emergency imposed by Indira Gandhi, and in the Lok Sabha election of 1977, he worked for the then Janta party under Morarji Desai.
He was elected from Gujarat to Rajya Sabha (Janta Party) from 10-04-1978 to 09-04-1984.