Quebec provincial police Sgt. Marc Tessier said the dead are two adults and two children who were travelling in the car.
"The driver of the truck was injured but we don't fear for his life," said Tessier.
The truck and car were travelling in opposite directions and police believe the car veered into the truck's lane just before the collision happened.
"It's too early to say what caused the accident," Tessier said, although he added icy road conditions may have been a factor.
The reserve is about 350 kilometres northwest of Montreal.