The teams started warily, poking and probing for openings, eager to hold onto the ball to do so which made for a crowded midfield that neither initially managed to dominate.
In the fourth minute Macrae pumped a longish ball goalwards but it did nothing to stretch Main.
Lawrence made a foray to the fringes of the Cans box but his shot on the turn was blocked before it reached the six-yard box.
In the 14th minute Mackintosh took a stravaig down the right wing before slipping the ball into Wood who sclaffed his shot wide right.
Greig was taking the ball to wide areas and began to stretch the visitors enough for one or two crosses to fly across their box and as the half progressed the wily McKeown began moving his rearguard further forward and began to compress the area ahead, starting the process of forcing the visitors onto the back foot.
In the 20th minute Mackintosh combined with Lisle and Wood to set himself up for a scorching drive that Knight, at full stretch, pushed away from the base of his right upright.
Rodger did likewise a minute later. United were getting the upper hand, winning a number of individual battles: Lisle was regularly skinning Hamilton, Mackintosh had the time and space of a time lord, and Wood was getting the better of Fraser.
Knight was busy dealing with shots from Rodger, Wood and Lisle while Dan Park had a couple blocked in the six-yard box.
A minute before the break McKeown thundered through the middle before slipping the ball left to Lisle, who delivered the ball precisely to Greig a bit beyond the corner of the six- yarder. The winger hammered the ball low and hard beyond Knight.
Forres tried to press after the interval but United still had better possession.
In the 53rd minute after pressure down the left, Greig flighted a neat cross over the Forres box to meet the head of Lisle, who crashed the ball home from about 10 yards out.
Forres were still in it even then but United were clearly the dominant force, maintaining a fair level of control.
With ten minutes to go they lost McKeown to injury but adapted well to the ten-man set-up, having used up all of their substitutes.
Such was their ball retention that United were still mostly in control.
Rodger proved that with superb solo goal, breaking down the right and leaving defenders in his wake before skelping an unsaveable drive past Knight in the 92nd minute.
United now sit fourth in the league, six points behind leaders Buckie Thistle and five behind second placed Fraserburgh with a game in hand over both. Brora Rangers sit third, three points better off than United.
After their Scottish Cup clash with Turriff United this weekend Formartine return to league action on September 28 at Lossiemouth.