Born Percy Frederick Beazley in Liverpool, England in 1881 to Irish parents, and educated at St. Xavier's Jesuit College in Merseyside, he headed for Ireland at an early age, and helped Richard Mulcahy, Patrick Pearse and other members of the IRB to infiltrate the Gaelic League, helping to force out the founder of the League, Douglas Hyde in 1915, the same year in which the Easter Rising was planned. Béaslaí fought in both the Rising and the Irish War of Independence. During the latter, he helped facilitate a mass escape of rebels from prison in Manchester. He was a cousin of Lily Merin (or Mernin), one of Michael Collins' moles in Dublin Castle, who passed much useful information to Collins, and pointed out undercover targets in the street.
Later Béaslaí became director of publicity for the Irish Republican Army, and at the 1918 general election he was elected to the First Dáil Éireann as Sinn Féin MP for Kerry East. In January 1919, Sinn Féin MPs who had been elected in the Westminster elections of 1918 refused to recognise the Parliament of the United Kingdom and instead assembled at the Mansion House in Dublin as a revolutionary parliament called Dáil Éireann.
At the 1921 general election he was returned unopposed to the 2nd Dáil as a Sinn Féin Teachta Dála (TD) for Kerry–Limerick West. He was re-elected unopposed at the 1922 election as a pro-Treaty Sinn Féin candidate. He did not contest the 1923 election, and in his latter years he dedicated himself to literature. He wrote a book about his experiences titled Michael Collins and the Making of a New Ireland (which was published in Dublin in 1926).
- Coogan, Tim Pat (1991). Michael Collins. Arrow Books. pp. 98–99. ISBN 0-09-968580-9.
- "Piaras Béaslaí Papers". National Library of Ireland. Retrieved 15 February 2013.
- Coogan, Tim Pat (1991). Michael Collins. Arrow Books. p. 93. ISBN 0-09-968580-9.
- "Mr. Piaras Béaslaí". Oireachtas Members Database. Retrieved 6 June 2009.
- "Roll call of the first sitting of the First Dáil". Dáil Éireann Historical Debates (in Irish). 21 January 1919. Retrieved 6 June 2009.
- "Piaras Béaslaí". ElectionsIreland.org. Retrieved 6 June 2009.
- "Con Collins". ElectionsIreland.org. Retrieved 6 June 2009.
|Parliament of the United Kingdom|
|Sinn Féin Member of Parliament for Kerry East
|New constituency||Sinn Féin Teachta Dála for Kerry East