The 20-year-old law student made a series of quality stops as the students edged Aberdeen 2-0 at Peffermill.
Forrester, who is also goalkeeper for Scottish Universities, received praise from his coach Graham Moodie.
Jay Harman netted Edinburgh's two goals but Moodie said: "David had a fantastic game. He carried on from Tuesday when we beat Watsonians 2-1 and his performance was exactly what we needed."
The result means Aberdeen play new Division Two winners CALA Edinburgh in the relegation-promotion play-off at Peffermill on Saturday.
Elsewhere, Inverleith lost at Peffermill to Western. Two goals from Andrew Sewnauth and an opportunist late strike by Dougie Simpson gave Western a 3-2 victory to clinch second spot in the league for the Glasgow club.
Under-strength Grange thrashed Menzieshill 6-1, also at Peffermill, as the Edinburgh club build towards their Scottish Cup semi-final showdown with champions Kelburne.
Already relegated Watsonians finished the season with a 5-2 home win over Aberdeen.