Parliament was convened for the swearing-in exercise.
Prof Oquaye was sworn into office in the absence of President Nana Akufo-Addo who left the country on Saturday, 27 January, 2018 for the African Union (AU) Summit in Ethiopia.
Vice-president Dr Mahamudu Bawumia is also in the United Kingdom on a sick leave.
This is the second time in a week the Speaker has been sworn in as acting president.
A section of Ghanaians have said swearing in the Speaker to act as president each time the president and vice-president are not within the jurisdiction of Ghana is needless.