The 20-year old opened the scoring in the ninth minute at Parkhead with he ran onto Anthony Stokes defence-splitting pass to slot home from 12 yards before Joe Ledley doubled the lead in the 33rd minute with a nice finish from another Stokes ball.
Ki Sung-yueng made it 3-0 in the 67th minute with a blistering 25-yard striker prior to Forrest’s second, just over 15 minutes from time.
The victory put the Hoops back to second after getting things back on track following a shock loss to Inverness Caledonian Thistle three starts back.
Leading the SPL pack is Rangers who won 1-0 away at Dundee United thanks to Kyle Lafferty’s 61st minute strike but the reigning champions really should have run out more comfortable winners after Terrors striker Johnny Russell was sent off on the half-hour mark for headbutting Kirk Broadfoot.
Elsewhere in Scotland, Inverness and Hearts played out a 1-1 draw with Gregory Tade and Stephen Elliott scoring the respective goals for their clubs, Paul Heffernand scored twice as Kilmarnock held off Dunfermline Athletic 3-2 at home whilst St Mirren and St Johnstone were involved in a scoreless draw in Paisley.