Operation unthinkable is the first thing that comes to mind when I think about the West invading the Soviets but as weird as it is, I never really hear anything about any Soviet attempt at conquering the rest of Europe.
The allies had Operation Unthinkable, the Soviet strategists deduced that such a plan probably existed and had defensive plans for such a scenario but generally speaking, neither side was ever close to actually going through with it.
I wrote about this about a year ago here, maybe it answers your question? (By me /u/superplaner, I see you Automoderator)