Defensive lineman Leonard Williams, linebacker Hayes Pullard and safety Su'a Cravens were selected along with receiver Nelson Agholor.
Williams has been selected to several preseason All-America teams and is regarded as a potential NFL first-round draft pick. Last season, he had 13 1/2 tackles for losses, including six sacks.
Pullard, a senior, is a returning team captain and the most experienced player on defense. Last season, he had a team-best 94 tackles.
Cravens, a sophomore, intercepted four passes and was a freshman All-American in 2013.
Agholor caught 56 passes, six for touchdowns, last season. He also returned two punts for touchdowns.
USC opens Aug. 30 against Fresno State.
Follow Gary Klein for USC football @latimesklein