1. That was the first time I had talked to Susan ourside the office.
2. That was the first time I talked to Susan ourside the office.
Are the both grammatically correct? If are, how are they different in the meaning?
They are both correct, and there is no real difference in meaning.
Are the both grammatically correct? YES
If they are, how are they different in the meaning? They're not.
John
Note - 'outside'