Posey added an RBI double and a single as the Giants overcame a three-run deficit.
The Reds scored three quick runs off Tim Hudson.
Hunter Pence started his second game after resting a sore shoulder. He tripled after Posey's home run.
Ehire Adrianza hit his second home run of the spring, a two-run shot off Cingrani, who allowed six runs after pitching seven scoreless innings, including the first two innings of this appearance.
Schumaker, who signed a two-year deal with the Reds in November, doubled and hit a solo home run off Hudson. He is hitting .550 this spring.
Its the Reds and Rockies Wednesday afternoon with the action at 3 35pm on Fox Sports 1360.