Coming off a four-point, 1-for-13 shooting performance Saturday against Washington, Joseph made 9 of 15, including 5 of 9 from 3-point range.
E.J. Singler scored 13 points for the Ducks (11-4, 2-1 Pac-12), who went 10 for 12 from the free throw line in the final 3 minutes.
Oregon is off to its best start since opening 12-4 in 2006-07 and is 9-0 this season when scoring at least 70.
Josh Owens led the Cardinal (12-3, 2-1) with 19 points. He had 17 points on 7-of-9 shooting in the first half but picked up his third foul early in the second and sat out nearly 7 minutes.
Aaron Bright also scored 14 points for the Cardinal, and John Gage added 13.
Oregon led 34-32 at halftime and never trailed in the second half.