The fire was reported along the 241 Freeway near Chapman Avenue and Santiago Canyon Road at Loma Ridge, near the Orange County Emergency Operations Center.
Santiago Canyon Road was closed in the area for emergency crews.
Two Cal-Fire fixed-wing aircrafts were assisting two Orange County Fire Authority water-dropping helicopters, according to the OCFA.
More than 100 firefighters were on scene.
The fire was reported about 4:30 p.m. It was believed to have begun about 4:10 p.m.
No injuries were reported. No structures were threatened.
By 6:15 p.m. the fire was almost entirely extinguished. Fire crews were expected to remain on scene through the night to ensure against flare-ups.
The cause of the fire was under investigation.