[1] He was brought up by the family of Admiral Robert Blake in Bridgwater and later became involved in trade through the port of Bristol.
[2] His first writings were poetry and dramas, among them being Amores Britannici; Epistles Historical and Gallant (1703); and a tragedy, The Governor of Cyprus.
His Critical History of England (1724-1726) contains attacks on Edward Hyde, 1st Earl of Clarendon and a defence of Bishop Gilbert Burnet, and its publication led to a controversy between Dr Zachary Grey and the author, who replied to Grey in his Clarendon and Whitlock Compared (1727).
From his exile, Atterbury replied to this charge in a Vindication, and although Oldmixon continued the controversy it is practically certain that he was in the wrong.
Oldmixon had much to do with editing two periodicals, The Muses Mercury and The Medley, and he often complained that his services were overlooked by the government.