Scorers: Wallace (Pen 55) and Beith (83 and 90+1)
THREE unanswered second half goals saw Stranraer take advantage of postponements elsewhere to move up to third in League One.
The Blues were simply too strong for a Forfar side who now sit ninth, only off bottom spot on goals scored.
Stevie Farrell's men had looked impressive on their travels over the last fortnight with three points at Arbroath and a point at East Fife.
And they followed up on that with a dominant showing against Forfar.
The Stranraer boss made one change from the draw at Bayview Stadium, with Scott Robertson replacing the suspended Liam Dick in the starting line-up.
Robertson slotted in at left back, with Jamie Hamill continuing in the other full back role.
Stranraer were almost, literally, handed the perfect start when referee Steven Reid pointed to the penalty spot with just nine minutes on the clock.
Defender Jamie Bain appeared to handle Ryan Wallace's corner, which gave Hamill the chance from the spot.
However, goalkeeper Marc McCallum was equal to the spot kick and then blocked Grant Anderson's rebound.
That was the best chance of the first half, with neither goalkeeper truly called into action.
Instead, it would be in the second half where most of the action took place.
Ryan Thomson and Ousman See, a half time substitute for Mark Millar, had shots dealt with by the goalkeepers before Stranraer had the ball in the net.
McCallum won the race to Thomson's ball over the top but appeared to spill it at the feet of Anderson.
The midfielder took advantage and rolled the ball into the empty net but the referee ruled McCallum had the ball in his hands and disallowed the goal.
Despite the goal not counting, it was exactly what Stranraer needed.
The home fans were firmly behind their team and encouraged them to right that wrong and get the goal.
They did not have long to wait and again Forfar played a part in the goal.
Kyle Turner's ball into the box was collected by Wallace, who went down under the challenge of Bain.
The referee again pointed to the spot and this time Wallace took responsibility from 12 yards.
He made no mistake in squeezing the ball beyond the ex-Livingston number one, although he almost came to his side's rescue for a second time.
It felt at the time like a match-winning strike but it would not be until the final ten minutes that the hosts put a bit of gloss on the scoreline.
Angus Beith had scored on his debut against Arbroath a fortnight earlier and was able to toast his first strike at Stair Park.
The midfielder gambled on Thomson's knock down and swept the ball past the advancing McCallum with seven minutes left to play.
Then, in stoppage time, he was on hand to finish a fine counter-attack.
Credit should go to Cameron Belford, who quickly got the attack moving by throwing the ball out to Paul Woods.
The substitute set up Wallace for the equaliser last week and was the provider again as his fine run and through ball found Beith, who again swept home.
On another occasion, a missed penalty and a goal chopped off might sound like the start of a hard luck tale for Stranraer.
However, the Blues were worthy winners after enjoying the bulk of possession and now turn their attention to Tuesday night's clash with Albion Rovers.
Stranraer: Belford, Robertson (McGowan 80), Barron, Neill, Bell, Wallace, Anderson (Woods 78), Turner, Beith, Hamill (Lang 86), Thomson.
Not used: Okoh, Gray, Stoney and McLaren.
Forfar Athletic: McCallum, Bain, Quigley, Whyte, Travis, McNaughton (Starkey 69), Aitken, Cregg, Milne, Easton (Peters 77), Millar (See 46).
Not used: Warwick, Allan and Adam.
Referee: Steven Reid