During the 12-hour network event, more than 10 million Australian individuals and businesses were unable to make calls, access the internet or complete transactions.
In response, the company apologised and customers - including businesses that lost thousands in sales - were offered 200GB of extra data, or free data on weekends if they were on prepaid plans.
The wrath of various senators will fall upon Ms Bayer Rosmarin when she fronts a committee on Friday morning to answer questions about the response during and after the November 8 outage.
Greens senator Sarah Hanson-Young, who will chair the committee, said Optus had handled the situation "atrociously".
"There's a lot of angry Australians and frustrated people - millions were impacted and people have a right to know that they can have confidence," she told Sky News on Friday.
"For the second largest communications company in the country, they're pretty bad at communicating."
While Deputy Opposition Leader Sussan Ley welcomed the inquiry, she said government ministers had questions to answer as well.
"(They) are really, really worried and anxious that when they pick up their phone, it's not going to work, and they need answers.
"I think government ministers need to be in the hot seat."
CEO Kelly Bayer Rosmarin says she will co-operate with all reviews into the Optus outage.
The Greens pushed for and secured the inquiry the day after the outage and Senator Hanson-Young vowed to examine Optus' responsibility to look beyond their profits and protect the public.
The Australian Communications and Media Authority has also begun its investigation of Optus' compliance with the rules on emergency calls.
Ms Bayer Rosmarin has said Optus will co-operate with reviews launched by the government and the Senate.
The company blamed the outage on a routine software upgrade, when changes to routing information cascaded through multiple levels of the Optus network.
It took longer than expected to restore the system because some of the routers needed to be physically rebooted, requiring Optus staff to be deployed to a number of sites across the country.
The outage came just over a year after Optus fell victim to cyber attack that compromised the data of millions of Australians and caused the Medicare, licence and passport numbers of 10,000 customers to be stolen and leaked online.
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