 For over 30 years Penfold lectured in Māori language at the University of Auckland and is believed to have been the first Māori woman to do so at a university in New Zealand.Her translations of nine of Shakespeare's sonnets into Māori were published in the book "Nga Waiata Aroha a Hekepia" in 2000.She was also a member of the editorial team for the seventh edition of Williams' "Dictionary of the Maori Language", published in 1971.