Professor Ohlmeyer is a passionate teacher of undergraduate History students and offers courses on the War and Society in early modern Ireland and Europe, the Nobility in the early modern period and the Civil Wars of the 1640s. She has supervised nine doctoral students on a wide variety of topics relating to early modern Ireland. Most of her doctoral students have received IRCHSS Government of Ireland studentships.

Professor Ohlmeyer is an expert on the New British and Atlantic Histories and has published extensively on early modern Irish and British history. She has recently completed Making Ireland English: the formation of an aristocracy in the seventeenth century for Yale University Press and volume 2 of The Cambridge History of Ireland is currently in the press. She is currently working on an edition of Edward Hyde, earl of Clarendon, A shorte view of the State and condicon of the kingdome of Ireland/The History of the Rebellion and Civil Wars in Ireland (Dublin, 1719/20 and London, 1720 and 1721) and a study of 'Colonial Ireland, Colonial India'. Professor Ohlmeyer is also an active proponent of 'Digital Humanities' Over the years Professor Ohlmeyer has attracted significant amounts of highly competitive funding for her own research projects and for her graduate students. She has considerable expertise in overseeing major editorial projects and helped to secure over 1M in funding from the IRCHSS, the AHRC (the UK funding council) and Trinity College for the digitization and online publication of the 1641 Depositions. She is a founding member of the Trinity Long Room Hub, Trinitys humanities research institute and serves its Internal and External Advisory Boards and in a related initiative. Creativity, the City and the University  which is linked to the Dublin Creative Alliance. She was closely involved in setting up the Humanities Serving Irish Society consortium which under PRTLI 4 secured funding for the Digital Humanities Observatory. She is also the Principal Investigator for the Trinity College Dublin element of Humanities Serving Irish Society which was awarded 10.78M as part of PRTLI 4.