Signs are to be erected at Culloden Battlefield asking visitors to respect the site as a war grave following a complaint about picnickers.
A member of A Circle of Gentlemen, a society which recalls the Jacobite cause, said he was furious at the behaviour of some tourists.
Alasdair MacNeill said he saw a family picnicking on top of one of the grave mounds.
The National Trust for Scotland (NTS) said it was aware of the issue.
Culloden, near Inverness, saw the defeat of the Jacobites in April 1746.
The circle takes its name from a secret society in Edinburgh.
It remained loyal to Charles Edward Stuart - Bonnie Prince Charlie - after the Jacobites' defeat at Culloden and continued to meet late into the 18th Century.
Mr MacNeill said he and other members had complained to the trust.
He said: "A family of four and their two dogs were sprawled across a grave mound having a picnic.
"The father was leaning against the headstone eating a Scotch egg and smoking a cigarette."
The circle member said he would not expect such behaviour to be acceptable at World War I battlefields such as Flanders or Ypres.
Mr MacNeill said Culloden's fallen were hastily buried in wide, but shallow graves, by British soldiers.
He added: "Many people - especially American tourists, come to Culloden because it is a revered place and to find their relatives."
NTS said it was taking action aimed at encouraging visitors to treat the battlefield with greater respect.
A spokeswoman said: "This is an issue we are aware of and we are currently having signs made up which explain that the battlefield is a war grave and asking visitors to behave accordingly."
Last month, the Queen became the first British monarch to set foot on the battlefield.
Archaeologist and Culloden expert Dr Tony Pollard said her visit was a "landmark" event in the history of the site.
Culloden was the last battle fought on British soil. It brought an end to a major military campaign by Bonnie Prince Charlie to claim the British throne.