The 27-year-old is seeded fourth in the Copper Box at the Queen Elizabeth Olympic Park and made it two wins in two days with victory over Taipei's Hsu Jui Ting.
Ouseph, who beat Ukrainian Vitaly Konov after a bye into the second round, defeated his younger third-round opponent 21-14, 21-12 in 34 minutes.
He will now face Zulfadli Zulkiffli of Malaysia in the last eight and is getting increasingly confident he can enjoy success at the inaugural London Grand Prix.
"I was probably a bit more comfortable in the hall than I was on Wednesday and I think his game style suited mine," said Ouseph, who failed to make it past the group stages at the London 2012 Olympics last summer.
"He is quite young, so he made a few mistakes that he wouldn't have made if he was older. So I managed to capitalise on those and it was comfortable in the end so I was quite happy.
"The conditions change day to day, so every day you need to get used to the arena as quickly as you can so you're comfortable and playing your own game.
"I'm probably favourite to win, but I've played Zulkiffli before and it was a three-game match, so we'll see how it goes."
- Sports & Recreation
- Queen Elizabeth Olympic Park
- Zulfadli Zulkiffli