Most of the mushrooms in the Twin Cities area are not poisonous, but be sure you check before letting your dog eat them. There is a great resource through Pet Poison Helpline to help you identify the type of plant (or mushroom).

http://newyork.cbslocal.com/2012/07/26/golden-retriever-puppy-nearly-dies-after-eating-mushrooms-from-backyard/

http://www.petpoisonhelpline.com/2012/04/new-iphone-application-and-mobile-enabled-website/