San Jose Fire Department Capt. Christopher Salcido says the beam fell off of a flatbed truck, crashing through the windshield and lodging itself into the driver's seat of the BMW.
The driver, 66-year-old Don Lee of San Jose, California, suffered a small scratch to his right arm.
Both vehicles were traveling at 60 mph when the incident occurred around noon Friday on I-280.
Twenty-two-year-old Javier Zambrano of Los Banos was driving the Ford flatbed truck carrying the beam. California Highway Patrol spokesman Ross Lee says Zambrano will be cited for spilling a load once the investigation is complete.