Born in Boston, Massachusetts, O"Connell attended the Mather School of Boston and prepared for college at Saint Mary"s Parochial School. O"Connell was graduated from Boston College in 1893 and from Harvard University Law School in 1896.
While at Boston College, O"Connell and Joseph Drum helped create the first Boston College football team O"Connell was admitted to the Suffolk bar in 1897 and commenced the practice of law in Boston. O"Connell was elected as a Democrat to the Sixtieth and Sixty-first Congresses (March 4, 1907 - March 3, 1911).
However in 1908 he was only reelected by 4 votes over former Boston City Clerk J. Mitchell Galvin.
He was an unsuccessful candidate for renomination in 1910. In a three-way primary with former Representative William South. McNary and Boston City Councilor James Michael Curley, O"Connell came in second behind Curley.
After his defeat O"Connell resumed the practice of law in Boston, Massachusetts. In 1916 the Massachusetts legislature and electorate approved a calling of a Constitutional Convention.
O"Connell served as delegate to the in 1912 and 1920.
O"Connell was an unsuccessful candidate as nominee to the United States Senate in 1930 and as a candidate for Boston"s mayor three years later. He was Professor of law and vice president of the board of trustees of Suffolk Law School in Boston. O"Connell died in Boston on December 10, 1942, three days after his 70th birthday and was interred at Saint Joseph"s Cemetery, West Roxbury, Massachusetts.
In May 1917 O"Connell was elected to serve as a member of the Massachusetts Constitutional Convention of 1917, representing Massachusetts" 12th Congressional District. O"Connell was appointed member of the National Conference on Uniform State Laws by Government. David I. Walsh on September 2, 1914 and was reappointed by every following Massachusetts governor until his death.
O"Connell served as member of the State commission to revise the charter of the city of Boston in 1923.