He graduated from Harvard College in 1722, and went into the commerce and shipbuilding business with his younger brother Josiah and brother-in-law Edward Jackson.In 1748, the Bethell, a merchant ship they owned, took out a letter of marque to protect itself from Spanish privateers during King George's War.The Spanish ship's cargo, consisting of 161 chests of silver, 2 of gold, and various valuable commodities, was brought safely back to Boston and valued at around one hundred thousand pounds sterling.[3][4][5] Josiah Quincy retired shortly after this windfall, while Edmund remained in business, entering into a partnership with his sons.[6] Quincy was also a Freemason, and was a member of Master's Lodge along with Richard Gridley.