When your mushrooms are ready to form, encourage fruiting out the small end of the bag by cutting the side hole, then folding the top down tightly and taping it, blocking air flow through the filter patch. This way the hole provides the only source of fresh air. This Phoenix Oyster specimen fruited just over three weeks from inoculation.
Harvest your mushrooms when the edges of one or more of the caps in a cluster have turned upward, completely exposing the gills. Gently pull the entire cluster off the block of substrate. If you let them go much past this point they will put their energy into spore production, not into growing more edible esh, and they will not keep as well once harvested.
Store them in the refrigerator, in paper (kraft or waxed) or cellophane bags. They will keep for a few days to a week. During this time they may dry somewhat, but will still be good to eat. In sealed containers they soften and spoil quickly.