PQ MNA Stéphane Bergeron asked several questions about Boulet's testimony at the Charbonneau Commission last week.
He wanted to know why Boulet said she was unaware of fundraising targets for Liberal cabinet ministers, when other ministers had said they were common knowledge.
Government house leader Jean-Marc Fournier answered the questions.
It was then that Boulet was seen making the gesture at Bergeron.
Boulet later apologized.
Boulet served as provincial transport minister from 2007 to 2010, and was re-elected in the spring.