The event was attended by members of the Royal Family and close friends of the monarch.
Charles was said to be in high spirits after a day packed full of engagements.
He and Camilla launched the Coronation Food Project at the South Oxfordshire Food and Education Alliance in Didcot, Oxfordshire.
The project will support food networks across the UK to reuse greater amounts of surplus food.
The royal pair met staff and volunteers and heard about the ways in which food waste can be used for social good.
The King also Charles hosted a Buckingham Palace reception to honour the work of nurses and midwives over the decades as part of the NHS 75-year celebrations.
