The Champions started well forcing two corners in the first minute. James Sharp almost opened the scoring after his 20-yard volley forced a stunning save from Forfar keeper Michael Brown.
It was Forfar however who looked hungrier in the early stages and in form winger Ricky Waddell brought out a save from Craig Nelson on 14 minutes.
The visitors continued to press and Paul Shields almost got lucky after a good run, but Nelson was equal to the task. Brechin retaliated and Stuart Callaghan's long-range effort went high and wide off Brown's left-hand post.
Just after the half hour mark Waddell hit a fantastic 20-yard drive cleanly, but it went straight at Craig Nelson who held well. The visitors almost took the lead five minutes before the interval after Mathu King's effort was desperately cleared on the line by Steven Ferguson.
Brechin started brightly after the break but it was Forfar's Paul Sheilds who should have made it 0-1. Shields found himself one on one with Nelson, but he failed to take it round the ex-Hearts and Partick Thistle keeper.
Forfar took the lead moments later however after a mistake in the Brechin defence. Waddell won the ball on the right, crossed for King and he struck from 10 yards.
It was 2-0 only a minute later when David McClune fired home from close range after Nelson had parried a Waddell shot.
The rout was completed when Barry Sellars played through Paul Shields and he fired home from a tight angle to dampen the home crowd's spirits.