I am visiting Calgary for a volunteer trip and the woman I was with insisted we check out Peter's for a quick lunch. I ordered a burger and Oreo milkshake (super healthy, I know). She had let me know that their milkshakes have a reputation of being the best in North America - that's lofty, but it may be true.
The burger was meh. The onion rings my friend ordered were meh. The milkshake was unbelievably good. It's thick, had big chunks of Oreo (without getting stuck in the straw) and I honestly couldn't put it down.
It's modeled after a 60's drive-in, which is super fun! Overall, I give it a three. Not sure I'd go again for food, but would definitely stop by for another shake.
If you're from out of the country: they do not take US credit/debit cards, so make sure you have cash or a friend with a Canadian debit.