Oppal has been hearing evidence since last October about why police didn't catch Pickton in the late 1990s and early 2000s, but the inquiry has been sluggish as dozens of lawyers lined up to cross-examine witnesses, some of whom spent days and weeks at a time in the witness box.
The slow pace combined with a series of delays have made it increasingly unlikely Oppal would be able to finish his work before the previous deadline of June 30.
Oppal, who is scheduled to hear closing arguments next week, asked to have until Oct 31 to write his final report. The province's attorney general announced Thursday she had agreed to that request.
However, Oppal did not ask for time to hear additional evidence.
"We've heard a lot of evidence and we have a lot of exhibits and reports that have been given to us, so we feel that we can move forward," Oppal said in an interview Thursday.
"All commissions of inquiry have timelines, and we need to work towards those deadlines. We have more than enough evidence from which to make findings and recommendations."
Last year, Oppal asked to be given until the end of 2012 to complete his work, but the province instead set his deadline for the end of June.
A number of families of Pickton's victims, their lawyers and the Opposition NDP have demanded Bond give Oppal more time, saying there are several witnesses that have yet to be heard that are important to understanding why police failed to catch Pickton as he murdered sex workers from Vancouver's troubled Downtown Eastside.
But Attorney General Shirley Bond has repeatedly rejected those demands.
"I am very concerned about ensuring that this report comes to a conclusion so that we can use the recommendations that will be provided to ensure that this kind of tragic circumstance doesn't happen again," Bond said on Thursday.
"The commissioner has assured me he has had the time required to understand the policing aspects that need to be changed."
Lawyers representing families of Pickton's victims have argued there are a number of witnesses that still need to be heard and he asked Oppal to add more than a dozen to the hearings schedule.
The list included Ross Caldwell, a police informant who implicated Pickton years before his arrest; Lynn Ellingsen, who told Pickton's trial about seeing him murder a woman on his property; Bruce Chambers, a former Vancouver police chief; Beverly Hyacinthe, a civilian RCMP worker who knew the Pickton family; and police spokeswomen Anne Drennan and Catherine Galliford.
The families also asked that Oppal hear from Pickton and his brother David.
Oppal rejected those witnesses and will write his report without their testimony.
Neil Chantler, one of the lawyers representing the families of more than two dozen missing and murdered women, said he was disappointed Oppal didn't ask for more time to hear evidence.
"We remain of the view that this commission was unable to complete its work du to the strict time limits placed on it by the province," said Chantler.
The inquiry has been beset by delays and controversies since its inception.
Critics argued that Oppal, a former Liberal attorney general, was a poor choice to lead the commission.
A number of community and advocacy groups pulled out of the process last year when the province denied their requests for legal funding.
The inquiry was put on a three-week hiatus earlier this year when an independent lawyer appointed to represent aboriginal interests resigned, citing concerns that First Nations voices weren't being heard.
And the inquiry was rocked by sexual harassment allegations in April, when the National Post newspaper published anonymous allegations directed at an unnamed member of Oppal's staff. Oppal appointed an independent lawyer to look into those allegations.
The inquiry is looking into why the Vancouver police and the RCMP failed to catch Pickton while he was murdering impoverished sex workers, despite receiving tips implicating the former pig farmer as early as 1998. Oppal is also examining why prosecutors declined to put Pickton on trial after he was charged with attempted to murder a prostitute in 1997.
Pickton was arrested in February 2002 and eventually convicted of six counts of second-degree murder.
The remains or DNA of 33 women were found on his farm. He once told an undercover police officer that he killed a total of 49.