In a statement issued on Tuesday, Mr McQuestin said he informed state president Greg Mirabella on October 21 he would not continue in the role after the election, regardless of the result.
He alluded to "internal challenges" but praised the campaign team and coalition leaders for achieving a 3.5 per cent swing towards the Liberals and potentially positioning the party to increase its total number of seats.
"I am particularly pleased with the outcome in the so-called teal seats, which in my view provides clear lessons for the party moving forward," Mr McQuestin wrote.
"Clearly, the Victorian division of the party is facing some significant challenges and I wish my successor - whoever they might be - all the very best."
The coalition is projected to win at least 25 lower house seats but may equal or just exceed its starting tally of 27, largely courtesy of the Nationals picking up three regional seats.
Mr Guy's successor is set to be confirmed next week, with the outgoing leader to call the Liberal parliamentary party room together to elect his replacement once a clearer picture emerges of successful candidates.
Former shadow attorney-general John Pesutto has confirmed he will nominate, along with sitting MPs Brad Battin, Ryan Smith and Richard Riordan.
"We've lost six of the last seven elections. That is simply not good enough in anyone's book. We have to rebuild the organisation," Mr Pesutto told AAP.
The former shadow attorney-general has his nose in front of teal independent Melissa Lowe in the race to win the marginal seat of Hawthorn in Melbourne's inner east.
In a social media post on Monday evening, Mr Battin confirmed he would nominate for the Liberal leadership and said Victoria needed a "new start".
Several Liberal MPs have also approached shadow transport infrastructure minister and upper house MP Matt Bach to suggest he consider standing.
It would mean Mr Bach moving to the lower house within three months of assuming the post in keeping with an internal rule, unless a majority of the partyroom agrees to amend its constitution.
Since Saturday's thumping loss, former Liberal premier Ted Baillieu has called on the party to weed out those seeking personal glory and ambition.
A Liberal, speaking on condition of anonymity, said they did not want to be part of a "team of losers" for possibly another eight years in opposition and it was time for renewal within leadership.
"It's about presenting the next generation of Liberal. The generation of the past have had an opportunity to do something about this and they've f***ed it," the Liberal told AAP.
Another said: "We of the party have become so aloof from normal Victorians. People think Liberals aren't (normal). That's what we've got to change."
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