Firefighters estimate the fire burned 50 acres. The fire was initially estimated to be 100 acres.
Residents reported seeing smoke around 3:30 on Monday afternoon.
In the area of the 73 Freeway off of Bonita Canyon, four water-dropping helicopters and 15 fire fighting units were on the scene.
No homes were damaged in the blaze, but the flames came up to the gates of some homes.
The cause of the fire is under investigation.
Another brush fire broke out in Tustin Foothills at 9:30 Monday morning. It was caused by downed power lines and was put out quickly.