Peng will take on Sabine Lisicki in the last four after the German enjoyed a 7-6 (7-1), 6-4 win over Magdalena Rybarikova, the Slovakian 14th seed.
Second seed Ana Ivanovic progressed to the last four with a 6-3, 6-3 win over Croatian veteran Mirjana Lucic.
Ivanovic will now face Daniela Hantuchova after the Slovakian Hantuchova, seeded fourth, overcame Alison Riske of the United States 6-2, 6-4.
"I'm very happy with the win," said Ivanovic, who will be playing in her first semi-final of the year.
Ivanovic, a former French Open champion, looked to be back in grand slam-contending form after winning Bali to conclude last year and then rising to number 17 in the world, her highest ranking since October 2009.
But her momentum stalled this season, losing early at several events, including both majors so far.
However, in three matches this week in Birmingham, she has yet to lose more than four games in a set.
"I'm just enjoying competing again," Ivanovic said.
"I have a lot of nice memories on grass courts. Since the first match this week, I've felt good about myself and my game. I'm just trying to enjoy it while it lasts and have fun out there."
- AFPTags: sport, tennis, united-kingdom, england