[1] He was born in the townland of Oatfield, Cappataggle, County Galway, to John Beegan, a herdsman, and Mary Stephenson.
[2] Beegan claims that he was active with the Aughrim Company, Ballinasloe Battalion, Galway Brigade, Irish Volunteers from 1917.
Taking the anti-Treaty side in the Irish Civil War (1922-1923), Beegan took part in several armed operations against National Army troops.
He was captured in August 1922, interned by the Free State government, took part in a 14 days hunger strike in October 1923 and was released in November 1923.
[5] In 1951 he was appointed to the position of Parliamentary Secretary to the Minister for Finance by Éamon de Valera's government.