John Rawdon managed estates in County Down and participated in Irish public life as the first Earl of Moira. He inherited his father's baronetcy in 1724, later entered the Irish peerage, and received the earldom in 1762. He married three times; his third marriage, to Elizabeth Hastings in 1752, established the household from which their son Francis later entered a separate military and political career. Rawdon divided his time between Montalto and Moira House in Dublin.

He promoted agricultural improvement, tree planting and the linen industry, served on the linen board, and regularly chaired Dublin Society meetings. The family welcomed linen merchants attending Ballynahinch market and supported charter schools. Their patronage also extended to religious visitors: when John Wesley was refused a local church in 1760, Rawdon arranged for a bellman to summon listeners to an outdoor meeting.

In the Irish Lords he protested irregular parliamentary procedure, opposed judges holding office solely at the government's pleasure, and criticized Lord North's ministry. He backed a regency for the Prince of Wales in 1788–1789 and joined the Irish Whig Club in 1789. His tenants thanked him in 1783 for allowing them to vote independently. His reform sympathies had limits: he opposed the Volunteers' parliamentary reform campaign and resigned his colonelcy rather than admit Catholics to his regiment. He died at Moira House in June 1793.