I log into Oracle using my own user account, which we can call my_account, and I am granted select privileges on all of the tables in the schema th
I am using EF 4.2 and found that I was able to use tables from another user/schema only when creating a new connection (using my_account) and using a filter when going through the Entity Data Model Wizard. Add app_schema to the Displayed Schemas filter (be sure to press Update).
Like CMarchan suggests, if I set the filter on the connection in the server explorer, it works for me there, but the EDM wizard does not see the connection when creating a new model (maybe just a "feature" in 4.2).
Once the EDM is created, it does allow me to add/edit tables from app_schema.