For nearly 50 years Grey was a leading member of the government of Exeter; he was an elector of the civic officers almost every year between 1366 and 1412 and continually influenced the affairs of the city as a councillor or official. His local standing was based not only on a flourishing export trade in woollen cloth, but also on his skills as a goldsmith. In 1364 he went surety for a fellow merchant, Roger Plenty, when the latter undertook to export wool to Gascony and bring back wine in exchange; and it was with Plenty that he was indicted for fraud in the collection of customs at Exeter three years later. In 1373 Grey shared the marriage of a local heiress, Joan Aleyn of Wonford, who, however, was abducted from her guardians. Six years later he was granted at the Exchequer the farm of the subsidies due for collection on all goods except wool, woolfells and hides passing through the ports of Devon and Cornwall, and in 1380 (during the first Parliament of the year) the farm, now to be shared with the other Exeter representative on that occasion, John Talbot, was extended for six years. The same two men were appointed shortly afterwards to collect the ‘ancient custom’ on wool. Grey made further appearances in the Exchequer in 1380 and 1383 to provide securities for the lessees of the manors of East Luccombe (Somerset) and Sheepwash (Devon).
Since in 1385 Grey was returned to Parliament for both Exeter and Barnstaple, he may well have been the man of this name who in earlier years had rented an area of pasture from the latter commonalty. Similarly, in 1391 he sat for both Exeter and Totnes, having some residential qualification in the latter town as a feoffee and, from 1380, owner of property there.