A final parliamentary vote on a bill to legalise same-sex marriage could come as early as Thursday.
The bulk of speeches wrapped up in the lower house late on Wednesday night, after sitting hours were extended for a second day to allow extra debate.
MPs, around 120 of whom spoke on the issue, will now get the chance to propose and consider amendments before voting on the legislation itself.
Several government MPs, including Prime Minister Malcolm Turnbull, have said they will support or at least consider changes to be put forward by their conservative colleagues - namely Andrew Hastie and Michael Sukkar.
The Greens have also indicated they will propose amendments.
Labor will oppose any change, as will cabinet minister Christopher Pyne who branded some of them "superfluous".
If the bill passes unchanged from the one that cleared the Senate last week, it will become law.
If changes are successful, the bill will have to return to the Senate for approval.
Liberal backbencher Kevin Andrews, who is against same-sex marriage, believes the bill contains very little protection for religion and belief.
The former cabinet minister told parliament marriage was a "natural arrangement" between a man and a woman and pre-dated politics.
"To claim that there will not be a range of adverse consequences for the freedom of speech, religion and parental rights ... is wrong," Mr Andrews said.
"A significant concern that millions of Australians have about these proposed changes to marriage laws is the manner in which the freedom of speech and religion is threatened."
Liberal colleague Sarah Henderson, however, is backing the change.
In an emotional speech, she recalled the struggles one of her closest friends - John Parker, a gay man - before his death earlier this year.
"He really wanted to see this change in the law," she said through tears.
"One of the last conversations I had with him, he just said to me: 'Hendo, just bloody well get on with it, OK?' I say to my dear beloved friend who I miss dearly: JP, that's what we are doing."
