An Australian woman accused of murdering her in-laws with a toxic mushroom-laced beef Wellington will face court in May, a magistrate ruled Monday.

Erin Patterson faces three counts of murder for allegedly cooking up a poisonous meal in July 2023 that killed her parents-in-law and the wife of a local pastor.

The 49-year-old is also accused of attempting to kill her estranged husband four times.

Magistrate Tim Walsh adjourned the case to May 7 for a "committal mention", part of the legal process for sending a person to trial.

Patterson appeared in Latrobe Valley Magistrates Court by video link from a small room in jail, wearing spectacles and a zip-up blue prison jersey, with her hair in a short ponytail.

She appeared calm, speaking only briefly to say she could hear the magistrate and to confirm who was representing her legally in the hearing.

Police have previously suggested the meal she served included death cap mushrooms.

Patterson allegedly cooked the beef Wellington in late July, serving her estranged parents-in-law Don and Gail Patterson, both 70, as well as local Baptist pastor Ian Wilkinson, 69, and his wife Heather, 66.

The two couples allegedly started experiencing food poisoning symptoms later that night and, with their health rapidly deteriorating, they sought the help of doctors at local hospitals.

Don and Gail Patterson and Heather Wilkinson died in the days following the lunch, while Ian Wilkinson eventually recovered after spending nearly two months in hospital.

Police said the husband, Simon Patterson, "became ill after meals" on separate occasions in 2021 and 2022, and charged Erin Patterson with four counts of attempted murder.

The alleged triple murder rocked the sedate farming town of Leongatha, about two hours' drive southeast of Melbourne.