In Toad for Oracle 11.6, go to Options | Editor | Execute/Compile in the solution below.
For earlier versions:
Sometimes you have to use version control to ensure that you have a full history of what was changed in your database. This is good and proper, but, what is there to stop a developer accidentally editing a database object via the Schema Browser → Open in Editorfacility? You now have an object in the database that doesn’t match up to the code in the script(s) under version control.
The solution is quite simple, there's a Toad Option for this. Got to View → Toad Options then select Editor/Compile on the left side and on the right side, uncheck the option Allow compiling when source loaded from database.
Now, whenever any attempt is made to compile an object via the Schema Browser, the attempt will be prevented. The only way to compile the object is to load (or paste) a script into the editor and compile from there.
Obviously, it's easy for a developer to disable this option again, but that would not be soemthing that they would do accidentally!