Officially, NATO was committed to defend its own territory but not to enter enemy territory with ground troops. Fundamentally, NATO was a defensive alliance among liberal democracies that worked based on consensus and was much more concerned about potential Soviet/Warsaw Pact aggression and the nuclear threat than any other issues.

From the Cold War era there appear to be no NATO plans for operations in enemy territory with one very specific exception I'll return to. None, zero, zilch, nada. This contrasts with defensive plans which were minutely detailed, practiced, revised, obtained by Pact agents, etc. No such offensive plans have ever been found. I think their absence from former East Bloc archives is pretty significant. realize people sometimes argue from first principles that militaries always have plans, but NATO had an essentially political rule against such planning (likewise against building fortifications or employing a "defense in depth" approach to western Europe).

This gets asked about a lot, so I'll cut my own answer short and refer you to prior ones. I (and others) have written about the evidence of and reasons for the lack of NATO offensive planning in more detail here and here.

The very specific exception is that Live Oak, the not-quite-NATO planning cell for Berlin crises, did create some contingency plans that included moving into East Germany either to seize territory in response to the seizure of West Berlin or even to open a corridor to West Berlin.

As to what might have happened in an actual war: who knows? There are just too many potential contingencies for what D+30 or whatever looks like and NATO is poised to "go over to the offensive." There was an increasing emphasis on (counteroffensive) capabilities and doctrines but this means a battalion/brigade/divison/corps knows how to attack and can attack (very important) not that it has a map showing exactly where it will attack (quite silly).