Manager Phil Lafferty says his AFC St Austell side "dug deep" as they beat Stanway Rovers 2-0 to reach the quarter-finals of the FA Vase.
Neil Slateford gave St Austell a first-half lead, before Rovers' Daniel Beeson was sent off just before half-time.
Martin Giles headed in St Austell's second, while Slateford and Stanway player-manager Danny Slatter saw red.
"I'm delighted for the players, who have dug deep yet again," Lafferty told BBC Radio Cornwall.
"I'm very proud, we're flying the flag for corn wall and it feels good."
The South West Peninsula League Premier Division side are the first Cornish club to make the quarter-finals of the FA Vase since Truro City won the title in 2007.
" we got the ball down and outplayed them," Lafferty continued.
"Today we had to match them in their physicality stakes and we dealt with it quite comfortably - and still managed to score two great goals.
"It's brilliant to be representing the county and the South West Peninsula League at the moment - and we look forward to the draw."
St Austell will host Hellenic League Premier Division side Ascot United in the last eight.