Barker was 1.96 m (6' 5") tall, dignified and scholarly in appearance. He was deeply evangelical and his teaching was based simply on the Bible. During his episcopacy of 27 years the number of churches and the number of clergy more than doubled. He published "Thirty-six Psalms with Commentary and Prayer" (1851), and "A Charge Delivered to the Clergy of the Diocese of Sydney" (1859). He was also a contributor to "The Supposed Sacrament of Penance", "A Course of Sermons" (1838); and "On the Rise of the Errors of the Church of Rome, A Course of Sermons" (1840).