The bill, which would make Ontario the first province to make menu labelling mandatory, will be introduced this winter after consultations with the food industry and health-care sector, said Health Minister Deb Matthews.
"It's going to be there right up with the price," she said. "That decision is made. We will have the calories on the menus and menu boards."
The consultations will look at things like which restaurant chains should fall under the rules, she said.
"We don't want this to capture the small mom-and-pop restaurants because it's a pretty big burden to put on them," she said.
Matthews said she'll also seek advice on how to reduce the marketing of unhealthy food and drinks aimed at children.
A government-appointed panel made both recommendations in March to fight childhood obesity.
It advocated for a ban on junk food and fast-food ads aimed at kids under the age of 12 and stopping the promotion and display of junk food at the checkout.
The number of overweight or obese children in Ontario has jumped 75 per cent over the last 30 years, according to the government. In 2004, 27.5 per cent of Ontario kids between the ages of 2 and 17 were overweight or obese.
It's a growing problem that's also taxing Ontario's health-care system, the panel said. Last year, the province spent $4.5 billion caring for people struggling with obesity.
More than 30 years ago, Quebec banned ads for toys and fast food aimed at children under 13 in print and electronic media — believed to be the first law of its kind. Other countries have followed suit.
Last year, a report looking at the impact of the law in Quebec found that it resulted in fewer children eating fast food and weighing less than their North American counterparts.
The New Democrats pushed for menu labelling and a junk-food ad ban for years, but the Liberals haven't committed to either until now.
Matthews made the menu announcement to distract people from a deepening scandal over their politically motivated decisions to cancel two gas plants before the 2011 election, the opposition parties said.
"The timing is not lost on me. I have brought this bill forward five times," said NDP health critic France Gelinas.
"I don't know how many scandals will happen, but I have way more ideas."
It's clearly an attempt to change the channel, said Progressive Conservative Leader Tim Hudak.
"(Premier) Kathleen Wynne does not want to admit that her fingerprints are all over the gas plant scandal, that she was there in the control room calling the shots," he said.
The Liberals also announced long-awaited legislation to ban minors from using tanning beds — which both a Liberal MPP and the Gelinas had urged for years — at the height of the scandal last year.
That bill passed unanimously Wednesday in the legislature.