The fast-food chain said it used the show to highlight its commitment to farming in Wales, where it currently sources produce from around 2,100 farmers, contributing around £1m to Welsh beef farmers.
The stand was aimed at providing farmers and visitors to the show the opportunity to find out more about McDonald's and ask questions. Visitors would also be able to take part in interactive displays on topics such as what goes into a hamburger.
Ron Mousey, a former farmer and now franchisee of McDonald's restaurants in Carmarthen, Pembroke Dock and Swansea, said: "Local sourcing is extremely important to McDonald's and we are committed to supporting Welsh farmers. We believe passionately in providing high-quality food using the best raw ingredients and I personally work with Welsh suppliers to encourage sustainable agriculture throughout the country.
"People are more interested than ever in where the food they buy comes from and the Royal Welsh Show is a great opportunity for us to let the public find out about our policies and the ingredients we use."