Once my son found a Morchella elata (spissmorkel) at Saraholmen (small island between Borøya and Kalvøya, Bærum), that wasn't in the autumn but in the spring. My wife and a friend was finding quite some chantarelles at the peninsula at Sandspollen. I don't think we did any mushroom hunting at Håøya, but I guess there is quite a lot there as well. On the very north tip of Jeløya, towards Bevøysund there are lots of wild strawberries.