Morita, seeded sixth, won the first seven games of her match before finishing off a 6-0, 6-4 victory over Zhang Shuai. Morita lost only two points on serve and won 61 percent of the points off Zhang's serve in taking control of the first set.
Jovanovski, the No. 8-seed, defeated Urszula Radwanska 1-6, 7-5, 7-6 in a match that took nearly 2 1/2 hours. Jovanovski dropped serve twice in each set but had three breaks in both the second and third sets in claiming the win.
Also Wednesday, Jelena Dokic overcame six service breaks in a 3-6, 7-6 (8-6), 6-2 win over Kurumi Nara and qualifier Anne Kremer got past Noppawan Lertcheewakarn 7-6 (7-4), 6-3 with seven breaks in 10 receiving games.
Jovanovski will go against Dokic in Friday's quarterfinals but Morita and Kremer will have to wait until Thursday's four second-round matches to learn their quarterfinals opponents.