The investigation, conducted by Maria Dew QC, was to review any evidence and probe allegations of sexual and racial discrimination, sexual harassment, bullying, and any misuse of drugs or alcohol.
The Herald understands the inquiry, which looked into allegations spanning back over the past three years, also examined how MediaWorks' human resources department handled and investigated complaints from staff members.
Wallace declined to comment on the report to the Herald last week and a spokeswoman said his focus would be on staff.
Dew also declined the Herald's request for an interview.
In the past month, details about a 2019 competition in which listeners of The Edge could join staff on an overseas trip have been removed from its website.
When asked if this was to do with the Dew inquiry, a MediaWorks spokesperson said "lots of old articles get taken down as we update our content".
"This was the case here as it features someone who now works at another one of our stations."
MediaWorks announced on March 14 it had commenced the internal investigation into allegations relating to its business after allegations of sexual harassment emerged on social media.
The external Dew inquiry was announced less than a week later, running in parallel to the company's internal investigation.
Later in March a radio host on one of the company's major shows resigned, and references to the host were removed from the MediaWorks website. Two staff members were also stood down.
The Rock radio station was put in the spotlight after four alleged incidents were shared on social media about the same employee.
One woman claimed the man "has been around forever creeping people out".
Another woman said she'd had "a few run-ins" with the man, and she would not feel comfortable being alone with him.
The first allegations prompted others to share their alleged experiences about other staff at the network.
Wallace told the Herald in April they were taking the allegations "very seriously" and was making sure the complaints weren't swept under the carpet.
"I'm committed to making sure MediaWorks is a fantastic commercial entity, but, just as importantly, that people feel safe, secure and proud of working here."