Pinchbeck United needed two second-half goals to continue their defence of the President Premier Shield.
Stand-in skipper Brad Murrell and top scorer Ollie Maltby were on target as they overturned ICA Sports’ advantage at Knight Street.
Pinchbeck – who saw off Moulton Harrox in last year’s final – booked their place in the semi-finals.
Player-manager Ian Dunn said: “We didn’t play at our best by a long stretch in the first half on Saturday.
“We didn’t get going on a heavy pitch which made it difficult to pass the ball.
“We gave the ball away in silly areas and it happened too often.
“Although they scored, we still created opportunities so it wasn’t all bad.
“We needed to cut out the mistakes and we made some changes at half-time.
“Within a minute of the restart Brad got onto a loose ball and fired into the bottom corner from 20 yards.
“After that equaliser, we dominated as their keeper made a number of saves and we hit the woodwork three times.
We deserved to win in the end and Ollie’s goal came from a bit of extra quality and patient play.Ian Dunn
“We deserved to win in the end and Ollie’s goal came from a bit of extra quality and patient play.
“Chris Shipley waited for the opening, he played a pass to Tom Panton who helped it on and Ollie scored.”
Goalkeeper Ben Martin made his debut after a loan deal with Wisbech Town as Joe Ashton has university commitments.
Captain Nick Bishop has an ankle problem which is again likely to rule him out of Saturday’s home game with Stilton United in the Premier Division.
Dunn added: “We had a lot of away games just before Christmas and now it’s evened itself out with home matches.
“By all accounts, Stilton acquitted themselves well at Nethrton United last time and only lost 1-0.
“So we expect them to make it difficult for us and get men behind the ball.
“We need to start well, be relaxed and take our time by not taking any risks.”
Meanwhile, defending champions Moulton moved into second spot with a 4-1 home win over Wisbech Town reserves.
Ben Allen (2), Dan Woods and Ashley Coddington were on target.
Langtoft United won 3-0 against bottom-of-the-table Uppingham Town thanks to Scott Spearink (2) and Ashley Firth.
Antonio Dello-Russo and Daniel Flood earned a 2-2 draw for Deeping Rangers reserves at Sawtry.