Formartine boss Paul Lawson was delighted after his side ended their Cove hoodoo.
United won 4-2 at the Balmoral Stadium to progress into the semi-finals of the Aberdeenshire Shield after the Highland League leaders had Connor Scully and skipper Eric Watson sent off.
Lawson’s side had been beaten in both the Aberdeenshire Cup and on league duty by Cove already this season.
The boss said: “The performance of the players was excellent.
“We’ve not got a great record against Cove, that’s no secret.
“It was disappointing to concede a goal at the end, but we’re pleased to be in the next round.”
Formartine got the opener after 12 minutes. Graeme Rodger was able to fire an uncleared ball past keeper John McCafferty and into the top left corner.
Jordon Brown’s shot off the post was Cove’s best effort before Garry Wood volleyed an Andrew Greig cross in at the back post to make it 2-0.
John Sheran’s men did pull a goal back against the run of play on 41 minutes, Harry Milne’s ball from the left wing coming off Jevan Anderson to tee up Daniel Park for a finish from a couple of yards.
Cove’s fightback was derailed after half-time when, on 54 minutes, Connor Scully was sent off for denying Graeme Rodger a clear goal-scoring opportunity after a poor McCafferty ball out.
McCafferty got a huge hand to Greig’s resultant free-kick but couldn’t stop the ball trickling in to make it 3-1.
United put it beyond doubt in the 62nd minute. With Cove committing men forward on the attack, the visitors broke and a long ball forward found Greig, who fired low and hard past McCafferty into the far corner.
To compound Cove’s misery, skipper Watson saw red after being adjudged to have stood on United keeper Kevin Main in the aftermath of a free-kick.
Cove did manage a consolation at the death, Jamie Masson cutting in off the left and firing a brilliant shot from the corner of the area into the far top corner of the net.
Cove boss John Sheran, whose team shipped as many goals as they have in 13 unbeaten league games, said: “We didn’t play well enough, simple as that.”
He added: “We can use it as a wake-up call – that if you drop your standard there are teams that will beat you.”
Sheran was unsighted for Watson’s red card, but thought Cove had players “coming in” to cover when Scully brought down Rodger.