More than 780 firefighters were on the line of the so-called White Fire earlier in the day. Some crews expected to stay on scene to mop up and monitor the area.
The fire burned 1,984 acres and destroyed two vehicles and a Forest Service garage.
At one point, 6,000 campers were forced out of the forest. Residents of the lower Santa Ynez Recreation Area have been allowed to return but visitors have not.
County officials said the cost of the blaze was estimated at nearly $2.9 million.
No injuries were reported. The cause of the fire was under investigation.
The Associated Press contributed to this report.