In the investigation, a group composed of three 18-year-olds and one 17-year-old was sent to four establishments. The CBC asked the three males and one female to order alcohol, but not to drink it if they were served. Provincial laws prohibit anyone under 19 years old from being served or sold liquor.
All four teens went together to Ebisu restaurant on Robson Street in Vancouver where they ordered a pitcher of beer and were served within minutes of sitting down.
The same night, the Keg Steakhouse & Bar on Still Creek Avenue in Burnaby served red wine to two of the 18-year-olds, who went in as a couple. Another Keg waitress served beer to the two other teens who were sitting in the bar area.
All four left their drinks untouched and later left.
Outside the restaurant afterwards, the teens offered their own theories about why they were served.
"It was just really casual,” said Jack Hu, 17. "I guess [the server] just thought we were older."
Aidan Ponton, 18, said he suspected the waitress sympathized with them.
"I guess she just saw us, just some younger kids and she knew what it was like, she'd been in that position before and she didn't hesitate," Ponton said.
Ben Roberts, 18, saw a monetary motive.
"They are making money off of it, a lot of money and I don't think that's their main priority to obey the law."
"[If] your employer's not forcing you to ID then you're not going to," said 18-year-old Katherine Gillard.
When later confronted with the results of the CBC News investigation, the management at Ebisu said they were shocked and embarrassed and promised to be more vigilant in checking identification.
A Keg spokesperson admitted its servers did not follow procedures and the restaurant chain will now redouble its training.
The teens also visited the Cactus Club and Boston Pizza, on Lougheed Highway in Burnaby. Both restaurants asked for government-issued identification and when the teens couldn't produce it, they were refused service.
The penalty for a first offence ranges from $7,500 to $10,000 or a 10-to-15- day licence suspension. Licensees can either accept the penalty or request an enforcement hearing.
CBC News has also learned the provincial government has recently begun doing its own secret spot checks of restaurant compliance with the law through its Minors as Agents Program. It found that 20 out of 29 restaurants — more than two-thirds — served alcohol to underage teens.