Bradford moved to Mount Hope Farm in Bristol, Rhode Island, where he was elected to the colonial assembly in 1761. He was elected to additional terms at various times up until 1803, and served as Speaker of the Assembly in several terms. He expanded his abilities with the study of law, was admitted to the bar in 1767, and established a practice at Bristol. He served as Deputy Governor of Rhode Island from November 1775 to May 1778. He served as major general in command of the colony's militia from June-October 1775 until being relieved by Major General Joshua Babcock. He was elected to the Continental Congress in 1776, but did not attend.