The 26 year old raced to the turn in 31 after starting on the back nine and then added another gain at the par five second.
At seven under through 11 holes, the former Amateur Championship runner-up led by two from England’s Garrick Porteous and Poland’s Adrian Meronk.
Porteous, who like Forrest enjoyed a glittering amateur career and is now looking to make his mark in the professional ranks after coming through Qualifying School for the third time, had five birdies over his first 15 holes.
Challenge Tour graduate Meronk started on the back nine and made three gains in his first four holes, before responding to a bogey at the 15th with a hat-trick of birdies to turn in 32.
South Africa’s Jaco Van Zyl was best placed of the home contingent on four under, alongside England’s Jack Singh Brar and Spanish pair Pablo Larrazábal and Alejandro Cañizares.