Quarterback Quinton Flowers got the Bulls out of an early stupor by passing for two touchdowns, both in the second quarter, and running back D'Ernest Johnson ran for two TDs, one on a 50-yard sprint.
Flowers completed 11 of 22 passes for 212 yards and also rushed for 70 yards and a touchdown before leaving the game early in the fourth quarter.
Six of his completions went to wide receiver Marquez Valdez-Scantling for 91 yards. Valdez-Scantling didn't score a touchdown but had a 50-yard catch that set up the Bulls' third-quarter score.
With Johnson and Darius Tice rushing for 99 and 94 yards, respectively, the Bulls amassed 315 yards on the ground and held the Spartans to 109.
Spartans quarterback Josh Love was 18-of-36 passing for 192 yards and two touchdowns, both to slot receiver Bailey Gaither. But Love also threw three interceptions, two of which led to South Florida touchdowns that turned the game around.
Backup Montel Aaron relieved Love and passed 22 yards to wide receiver Justin Holmes for the Spartans' final touchdown after Flowers scored from 1 yard to give the Bulls a 42-16 lead early in the fourth quarter.
The game got off to an auspicious start for the Bulls.
Kicker Emilio Nadelman's opening kickoff went out of bounds, punter Jon Hernandez's first punt went only 18 yards and set up a Spartans' field goal, and defensive tackle Deadrin Senat was ejected for targeting -- all in the first seven minutes.
In the rest of the first quarter, they had a punt blocked that led to a San Jose State's second touchdown and Flowers was sacked three times.
When the quarter ended, the Bulls had only 23 yards in total offense -- all rushing -- to 95 for the Spartans and managed only one first down. They trailed 16-0 after Gaither hauled in his second touchdown pass with 3:11 left in the quarter.
But it all turned around in the second quarter, which ended with the Bulls going to the locker room up 28-16.
NOTES: After the miserable start, South Florida had 270 yards of total offense in the second quarter. ... Coach Brent Brennan didn't announce sophomore Josh Love as San Jose State's starter at quarterback until just before the game. ... San Jose State offensive coordinator Andrew Sowder was a quality control assistant on USF coach Charlie Strong's staff at Texas last year. He also worked with USF offensive coordinator Sterlin Gilbert at Eastern Illinois and Bowling Green. ... The Bulls opened their 21st season of football with their second trip to California. They lost at San Diego State 41-12 in 1999.