Peng was a 6-4, 6-3 winner over sixth-seeded Marion Bartoli. Bartoli grabbed 3-0 leads in each set but Peng answered each time. She won the last three games of the first set and six straight in the second to advance to the second round.
Ivanovic topped No. 7-seeded Francesca Schiavone 6-1, 7-5. She had 23 break-point opportunities over nine games, finishing off two in the first set and three in the second.
Fifth-seeded Agnieszka Radwanska escaped with a 6-1, 6-7 (6-8), 7-5 win over Aleksandra Wozniak in a match that took more than 2 1/2 hours. She had at least two breaks in each set.
Qualifiers Simona Halep and Iveta Benesova Tuesday moved into the second round against seeded players. Halep defeated Anastasia Pavlyuchenkova 6-4, 6-2 and will go against No. 3-seeded Caroline Wozniacki. Benesova was up 3-1 when Dominika Cibulkova retired with a hamstring injury. Benesova next draws ninth-seeded Sabine Lisicki.
Also Tuesday, Daniela Hantuchova edged Polona Hercog 1-6, 7-5, 7-6 (7-4) and Lucie Safarova beat Petra Martic 6-3, 5-7, 6-3.