As far as I am aware the 'modern' form of the Coronation Oath stems from the 1688 Coronation Oath Act passed in the first year of the reign of William and Mary. Under the provisions of that Act, the monarchs, like Queen Elizabeth II, swore to uphold the statutes of Parliament, the laws and customs of the land, the Protestant religion as established by law, as well as to 'cause Law and Justice in Mercy to be Executed...'
As we can see from what Nellie has posted regarding the wording of the Oath taken by Queen Elizabeth II, slight variations have been incorporated to include Commonwealth nations and the then existing colonies. In essence, however,the Oath is the same.
Does anyone know what type of oath the Tudor and Stuart monarchs might have taken?