"Preferred qualifications for admitted OMS CS students are an undergraduate degree in computer science or related field (typically mathematics, computer engineering or electrical engineering) from an accredited institution with a cumulative GPA of 3.0 or higher. Applicants who do not meet these criteria will be evaluated on a case-by-case basis; however, work experience will not take the place of an undergraduate degree."[0]
So unless that other field is Math or computer-related, then that's not really going to work, which is why I specifically mentioned "another field".
That appears to be a soft requirement. If you check out the admission thread on the subreddit[0], there is always a decent amount of students getting accepted with backgrounds outside the realm of computing and mathematics. That being said, there are plenty that don't make the cut as well. It's worth a shot for a cheap masters from a well-respected institution though.
I currently am taking this course. It's one of the best, and I get to learn a ton.
Coming to specifically the question, if you need a BS in Computers, then from personal experience, yes, your changes are much much higher if you already have BS.
If you don't, then they'll look into your SOP and related work to see if you good exposure to Computers.
So unless that other field is Math or computer-related, then that's not really going to work, which is why I specifically mentioned "another field".
[0] - https://www.omscs.gatech.edu/program-info/admission-criteria