Born in Yorkshire, Barker was trading in London by 1569 at the sign of the Grasshopper in St Paul's Churchyard. He secured an important and lucrative royal printing patent in 1573, becoming the first in England to print the Geneva New Testament (1575). Barker printed Protestant works, including two by John Foxe. With six presses in 1586, Barker's was the largest printing office in England.
From The Oxford Companion to the Book in Oxford Reference.