Foley was returned unopposed as Member of Parliament for Herefordshire at a by-election on 18 May 1767 and retained his seat at the 1768 general election. At the 1774 general election he was returned as MP for the family borough of Droitwich until he succeeded to his father's peerage in 1777. Foley was a close friend of Charles James Fox, and was a gambler. Mrs Delany a society gossip, wrote in 1773 "Mr. T. Foley has lost at Newmarket etc. fifty thousand pounds. He has now entered into an agreement with his father, that if he will pay his debts he will entirely leave off gambling." In November 1775 George Selwyn wrote "Old Foley pays another £70,000 of debt, and settles, I hear today, £4,000 in present upon his son, and £6,000 a year more at his death." Foley married Lady Harriet Stanhope, daughter of William Stanhope, 2nd Earl of Harrington, on 20 March 1776. He was appointed joint Postmaster-General in 1783 for nine months.
