He was senior moderator in history and English literature in 1856 and won that year's Dublin University prize for political economy.

He was curate at St Mary's, Kilkenny, from 1858 until 1861, then for two years took up the position of secretary to the Hibernian Church Missionary Society.

He became a canon of St Patrick's Cathedral, Dublin,[2] he was awarded the degree of Doctor of Divinity in 1883, and for a few months in 1894 he held the professorship of pastoral theology in Trinity College.

According to the Oxford Dictionary of National Biography, his reputation was for "tolerance, holiness, and varied pastoral experience" and also as "a man of fine presence".

[4] A portrait in oils of Peacocke by Philip de László (working sketch illustrated) was presented to him by the diocese and is now to be seen in the bishop's palace at Dublin.