The behind closed doors session will give members of the Scottish Secondary Teachers' Association (SSTA) an opportunity to discuss the shock decision to dismiss Sheila Mechan after only three weeks in the job.
In April, a union spokesman described the decision as "regrettable but necessary" after the breakdown of "crucial working relationships" between Ms Mechan and other officials.
However, Ms Mechan is still considering legal action over the decision,.
She said it had not given her the opportunity to develop her role.
Alan McKenzie, the current acting general secretary, who has taken over until a permanent successor is found, will tell members at the annual congress today that the issue will be discussed in private.
The only reference to the sacking of Ms Mechan in his speech is expected to be a reference to continuing good working relationships with the rival Educational Institute of Scotland (EIS) teaching union and its general secretary Larry Flanagan.
In the aftermath of her sacking Ms Mechan accused the SSTA of being "obsessed" with the EIS to the detriment of its own members.
However, Mr McKenzie is expected to tell the congress in Peebles: "We also continue to work closely with our colleagues in the EIS.
"I can only commend the open and frank attitude of the EIS general secretary and the support he has given me in difficult times.
"The message that we send is clear. We wish to continue to strengthen our relationship with you in spite of messages... by former employees."