She trained at the Abbey Theatre and first appeared on stage there in 1944. McAnally and Masterson had four children. Conor, Aonghus, Máire and Niamh.
They formed Old Quay Productions, which presented an assortment of plays such as Who"s Afraid of Virginia Woolf?, The Odd Couple and many others
Masterson had also played in the Edinburgh International Festival and in many Dublin Theatre Festival productions. She has appeared on many series broadcast on Raidió Teilifís Éireann, British Broadcasting Corporation and Independent Television and toured extensively in the United States in her own one woman shows.
She made her film debut in 1988, playing Bridie in The Dawning.