The probe says McGuinty is slated to appear Sept. 12 to close out Part 2 of the probe into the tragedy.
The second phase of the inquiry is looking at the emergency response to last June's collapse that killed two women.
Other staff from the Ontario premier's office slated to testify include a former senior communications aide, Wendy McCann.
The first part of the inquiry looking into the cause of the collapse is expected to complete its witness hearings in July.
To date, the hearings have heard about sloppy construction and ongoing leaks that ultimately led to the roof-top parking deck crashing down into the mall.