Welterweight Fred Evans and flyweight Andrew Selby are through to the Olympic quarter-finals after both won at the ExCel arena on Friday.
Six of the seven-strong GB men's team are still in the competition, after
Joshua Taylor exited on Thursday.
Evans beat Lithuania's Egidijus Kavaliauskas 11-7, while fellow Welshman Selby beat Ilyas Suleimenov of Kazakhstan 19-15.
Belfast flyweight Michael Conlan also triumphed 19-8 over Duke Micah.
“The Canadian looks a handful, is a strong kid, but I'm confident I can get the win and come away with a medal”
Ireland's Adam Nolan is out of the welterweight competition, beaten 18-9 by Andrey Zamkovoy of Russia.
Evans, who beat Algeria's Ilyas Abbadi in his first-round match on Sunday, barely threw a punch in the first round as both men felt each other out.
However, Evans started to get his jab working in the second before opening up in the final round, landing with left crosses and snappy right hooks at will.
The Cardiff southpaw faces Custio Clatyon in the last eight after the rugged Canadian beat Australian Cameron Hammond 14-11.
"I was expecting him to come straight at me but he stepped off and it got a little bit cagey," said Evans of the man who stopped him in last year's World Championships.
"What an excellent final round by Fred. I'm really pleased for the kid. He had to be a bit busier as the match continued but he was patient. It was well deserved."
"But I caught him early in the last round a few times and that's what made him come on and allowed me to open up. It was a terrific last round and I'm so happy I've pulled it out.
"The atmosphere is unbelievable.Sunday was a big shock, but I felt a bit more comfortable this time because I knew what to expect.
"The Canadian looks a handful, is a strong kid, but I'm confident I can get the win and come away with a medal."
Selby, the second seed and European champion, had a tougher time of it against Suleimenov, getting caught far too often in what was a scrappy affair.
The 23-year-old switch-hitter from Barry showed what he could do in the second round, when his movement and punching were in synch, but he would have been disappointed with his boxing on either side of that.
Selby next faces Cuban Robeisy Ramirez Carrazana, who beat Thailand's Chatchai Butdee in the quarter-finals.
American flyweight Raushee Warren and welterweight Errol Spence, also of the US, both went out after close contests. However, Spence has been
reinstated at the expense of Krishan Vikas.
Vikas was originally awarded a 13-11 win over Spence, but the sport's world governing body has overturned that verdict.
The Indian fighter should have had been penalised for holding and spitting out his gumshield, the appeal found.
Warren was beaten 19-18 by Frenchman Nordine Oubaali, while Spence went down 13-11 to Krishan Vikas, leaving heavyweight legend Evander Holyfield, a bronze medallist in 1984, shaking his head up in the stands in dismay.
In Evans's 69kg division, world champion and top seed Taras Shelestyuk looked untroubled in coasting to a 15-7 win over Moldova's Vasilii Belous.
Russia's Misha Aloian, who beat Selby by a single point to win last year's World Championships final in Baku, beat Algeria's Samir Brahimi 14-9.
In one of the fights of the afternoon session, Mongolia's Tugstsogt Nyambayar pipped number four seed and Beijing bronze medallist Vincenzo Picardi 17-16.