Culture Minister Helene David was about to speak to reporters when the woman jumped in front of the cameras, exhibiting her breasts and denouncing Bill 20, legislation opponents say will restrict access to abortion services in the province.
"No to Bill 20!" she shouted. "Abortion a priority!"
The woman obtained a temporary press card to gain access to the national assembly under the name Neda Topaloski, who is known for her ties to the international feminist group Femen.
The activist, who was ejected from the Commons in March for protesting against Ottawa's Bill C-51 anti-terror legislation, had "Priorite IVG" written on her chest. The letters stand for "interruption volontaire de grossesse" or voluntary termination of pregnancy.
A security guard forced the woman out of the room a few seconds after she had burst in.
Premier Philippe Couillard said in late March that Bill 20 would actually increase access to health services, including abortion.
The Femen group has protested in Quebec City before, notably when several members shouted in the national assembly to denounce the proposed secularism charter of the previous Parti Quebecois government.