Peterson sank seven of 11 shots with three three-pointers for the Trojans (14-6, 6-3 Pac-12). He added eight rebounds and four assists. Ellis hit four three-pointers, grabbed six boards and handed out four assists. Tre White contributed 12 points and seven rebounds before fouling out. Vincent Iwuchukwu had 12 points and five rebounds off the bench.
Warren Washington tallied 21 points and eight rebounds to pace the Sun Devils (15-5, 6-3). Desmond Cambridge Jr. scored 17 but made just three of 11 from three-point range.
USC used a balanced scoring attack — getting nine points from Ellis and eight each from Kobe Johnson, White and Iwuchukwu — to take a 43-33 lead at halftime.
Peterson, who scored 15 of his 19 points after the break, sandwiched a three-pointer between two Ellis baskets as the Trojans scored the first seven points of the second half and were never threatened. An Ellis dunk gave USC its biggest lead 77-53 with 4:35 left to play.
USC beat Arizona State for the sixth straight time. The Trojans are now 10-0 when their tip-off time is 7 p.m. PST or later.
Arizona State has lost two straight after a four-game win streak.
The Trojans, who hold opponents to 38.5% shooting — 10th best in the nation — held ASU to exactly that (25 of 65).