I had this infamous error when updating from AS 0.8 to Android Studio 1.0 RC4.
I saw already the question here: Could not find property 'outputFile' on com.android.build.gradle.internal.api.ApplicationVariantImpl and tried to adapt the code but with no success.
So I tried by commenting out the applicationVariants not to have this outputFile declared anywhere but still get the error (?)
Then I invalidate the cache using the option in File-> Invalidate Caches / Restart but again with no effect.
Finally i deleted the .gradle directory in my project folder but still got the error when trying to synchronise.
Do anyone have other suggestions on how to fix it?