He was educated at Jesus College, Oxford, from 1592 to 1596 and then, after some studying abroad, was appointed to the sinecure position of rector of Llansantffraid-ym-Mechain, Montgomeryshire, Wales.
Richard Vaughan, the bishop of London, appointed him as his domestic chaplain in 1605; Powell became rector of Chellesworth, Suffolk, England, in 1606 and ceased to hold the parish of Llansantffraid-ym-Mechain after 1607.
In 1609, he was made a prebendary of St Paul's Cathedral, London and in the following year he became the vicar of Northolt, Middlesex.
[1] Powell was a strident anti-Catholic and wrote a number of works condemning the Roman Catholic faith and its followers.
Whilst this language was condemned in later years by Archbishop Laud, his views were regarded as orthodox at the time and his writings were admired by contemporaries.