Lincecum, scheduled to pitch the Giants' third game of the season against the Los Angeles Dodgers on Wednesday, was masterful in a steady drizzle, keeping Oakland off balance.
Lincecum's performance was a needed lift for the Giants, who snapped a five-game losing streak that included a loss to Fresno, their Triple-A affiliate on Wednesday.
In his last three outings, Lincecum has struck out 20 batters.
The game was the first for the A's since they returned from Japan, where they split their first two regular season games against the Red Sox.
During the early innings of the game, a steady drizzle fell drenching the players and field.
San Francisco scored their two runs in the fifth when Daniel Ortmeier scored from second after Brian Bocock looped a single to center. The ball skipped away from A's center fielder Carlos Gonzalez on the wet grass.
The Giants scored their second run of the inning when A's starter Greg Smith threw a wild pitch, allowing Bocock to score.
Smith went five innings and gave up two runs -- one earned -- and five hits while striking out three and walking none.
The Giants added their third run in the seventh when Jose Castillo singled home Ortmeier.
