Mr Grieve, who has one of the most formidable legal minds in parliament, spent the past few months pushing for a "meaningful vote" amendment in the House of Commons on the Brexit deal due to be secured by Theresa May.
Pro-EU legislators accuse the government of going back on its word.
A video grab from footage broadcast by the UK Parliament's Parliamentary Recording Unit (PRU) shows Britain's Prime Minister Theresa May as she speaks during Prime Minister's Questions (PMQs) in the House of Commons in London on June 20, 2018.
Over 22 Conservatives reportedly voted against May's government.
And if the European Union can not agree on terms, Britain will leave next March deal-less.
Some of her opponents on Brexit may simply have chose to save their energy for later fights on issues such as future trading ties and customs arrangements with the bloc before Britain's scheduled departure in March next year.
After pro-EU Conservative lawmaker Dominic Grieve said he would support the government's proposal for a "meaningful vote" for parliament on any Brexit deal, a potential rebellion that could have further undermined May's authority looked to have been quashed.
May's government is divided between Brexit-backing ministers such as Foreign Secretary Boris Johnson who support a clean break with the European Union, and those such as Treasury chief Philip Hammond who want to keep closely aligned to the bloc, Britain's biggest trading partner.
The amendment now returns to MPs in the elected lower House of Commons, where Conservative rebels will ally with opposition parties in a bid to finally make it law.
The European Parliament's leader on Brexit, Guy Verhofstadt, said Wednesday that he remains hopeful a U.K. -EU withdrawal agreement could be finalized by the fall so national parliaments have time to approve it before March.
Worldwide trade secretary Liam Fox said nothing had really changed and the option of a no-deal Brexit had been left firmly on the table.
"The vote will be tight", a government source told AFP.
And despite the fact that she did compromise even in a meaningless way (yes I can't believe that I did just write that sentence, but it is relevant), the vote was still relatively close, certainly not comfortable enough for the government to relax any time soon. The government hailed its parliamentary victory as an important step to the United Kingdom regaining control "of its money, laws, and borders".
Downing Street's determination to force their motion through was indicated when Tory whips made clear they would not abide by a parliamentary convention allowing votes to be "nodded through" from ambulances and cars in the courtyard outside if MPs are too ill to physically pass through the voting lobbies. The upper house of parliament later approved the bill, paving the way for it to become law after gaining formal "Royal Assent" from the Queen.