Mr Grayland (52), of Alexandra, a former policeman and St John paramedic, died on September 3 while carrying out a controlled burn-off on Northburn Station, near Cromwell.
A WorkSafe spokesman said the prosecution followed an investigation into the incident.
The the charge, laid under the Health and Safety in Employment Act, was of failing to take all practicable steps to ensure an employee's safety.
The spokesman declined to identify who had been charged, as the matter was yet to come before the court and ''the party'' charged might seek name suppression.
The case will be called in the Alexandra District Court on May 19.
Following the incident, police said Mr Grayland and another man had been carrying out the burn-off.
The co-worker lost contact with Mr Grayland as the burn-off progressed.
The co-worker became concerned and contacted emergency services.
Mr Grayland was described by friends and former colleagues as a ''leader of men''.
His involvement in St John spanned 22 years and he had served as a paramedic as well as Central Otago district operations manager.
Before that, he worked for about 15 years as a police officer, based in Mataura, Middlemarch and Lawrence.
He was a stalwart of the Alexandra Pipe Band and carried out volunteer work for The Terrace School in Alexandra for many years.
Mr Grayland's widow, Rose, declined to comment yesterday on the prosecution.
Northburn Station owner Tom Pinckney was overseas and could not be contacted for comment.
WorkSafe NZ is New Zealand's workplace health and safety agency.
