Edward entered the Inner Temple in 1555, and had returned to Ireland to practice at the Irish Bar by 1563. He was justice of the Liberty of Wexford and Commissioner for Munster. In 1570 he was made Attorney General, and in 1574 he became Serjeant-at-law, holding that office until his death in 1593. In 1578 when the controversial judge Nicholas White was removed from office as Master of the Rolls, Fitz-Symon replaced him. He was a surprising choice since serjeants in that era rarely became judges, due largely to QueenElizabeth's low opinion of her Irish law officers. In any case the appointment was only a temporary one since White was restored to office within a few months. We have some glimpses of Fitz-Symon's official work: in 1577, during the height of the "cess" controversy, concerning the power of the Crown to levy taxes on the Anglo-Irish gentry of the Pale for the upkeep of military garrisons, the Lord Chancellor of Ireland, Sir William Gerard, called on him to give an important opinion on the royal prerogative. On another occasion he was asked to advise on a commission to reform the customs at Chester, but refused on the ground that he did not have adequate time. Gerard was clearly unimpressed by Fitz-Symon's abilities, calling him a man "of mean learning". Fitz-Symon pleaded regularly before the Court of Castle Chamber, the Irish equivalent of Star Chamber, and often sat in a quasi-judicial capacity. In 1572 he sat on a commission to inquire into the extent of the former lands of the O'Doyne clan, and decide whether they should be incorporated into Queen's County. Later the same year he sat on the commission to oversee the muster of troops in Dublin. In 1584 he served on a commission to inquire into all persons who had been attainted for treason in seven counties, and in 1588 sat on a commission to inquire into what lands in Sligo were held from the Queen by the Clan O Connor Sligo. Fitz-Symon is said to have made a considerable fortune: he owned the manor of Baldoyle, and in 1575 he sent £100, then a very large sum, to his son Christopher, who was a student in London. He died in 1593.
Religion
As an office holder, Fitz-Symon was obliged to conform in public to the Church of Ireland, and to swear an oath acknowledging Queen Elizabeth as the rightful Head of the Church, but his real sympathies were with the Roman Catholic faith. His son Christopher wrote to him from London in 1581 to say that he had temporarily left the Inner Temple, due to the recent establishment of a commission inquiring into all barristers and students who did not attend Anglican service. Clearly Christopher, an open recusant, expected his father to share his views on the matter.