Dani Venn, Alana Lowes, Kate Bracks and Michael Weldon were challenged to re-create a Maggie Beer chicken terrine in last night's episode but all four served raw chicken.
Judges Matt Preston, George Calombaris, Gary Mehigan and Beer revealed that they could not eat some of the dishes for health and safety reasons, with Preston adding: "If a dish comes to your table in a restaurant and the main element is raw, you send it back - you're not happy."
All four of the contestants will now face elimination rather than the previously-planned bottom two.
The grand final of this year's MasterChef is scheduled to take place next week.
This year's season of the cooking reality television show has been plagued with controversy. The judges and producers were forced to hit back at reports that they were mistreating the contestants, while former top ten competitor Mat Beyer was kicked off the show after being caught with a banned smartphone.
Finalist Kate Bracks also caused outrage when she refused to address the Dalai Lama as "Your Holiness" because she is a Christian.