He was engaged in mercantile pursuits, and with his younger brother,
Clement Biddle, signed the Non-importation Resolutions of October 25, 1765. He was a delegate to the Provincial Conference January 23, 1775; member of the Committee of Safety from June 30, 1775, to July 22, 1776, during which period he served as
de facto Governor of Pennsylvania on July 4, 1776, again on July 8 and 10, 1776, and finally on July 16, 1776. Owen Biddle continued service with the newly constituted Council of Safety from July 24, 1776, to March 13, 1777. He became a member of the Board of War on March 13, 1777, and was a member of the
Pennsylvania Constitutional Convention of July 15, 1776. In June, 1777, he was appointed Deputy Commissary General of Forage, with the rank of Colonel, by the Continental Congress. He served under his younger brother, Clement, who was the Commissary General of Forage and also a Colonel, until August 15, 1780. He and his brother labored for three years to obtain provisions for the Continental Army's horses, mules and other draft animals, while struggling to obtain funds, working with unreliable subordinates, and many unresponsive farmers. ==Astronomy and science==