When she joined, Oxtoby signed a four-year deal with NI, who had just competed in their first major tournament at Euro 2022 and transitioned into a full-time set-up.
It was a left-field appointment because she had a range of experiences including roles as assistant manager at Scotland, Chelsea and Australia’s under-20s.
The job was a big one - staffing was small, resources were sparse, the structure was new and the squad was ageing. She faced challenges as a result.
Oxtoby was critical of conditions NI faced on their travels and she had to lower the average age of the squad from 26.7 to 24.8 as part of the transitional period.
By the end of her tenure, a higher percentage of NI's squad were playing in England or Scotland, with just nine players domestic-based from the squad in October.
"I probably didn't realise exactly what I was walking into in terms of where it was at," Oxtoby admitted.
"I'm super proud of what I did there - the transition of the squad and bringing younger players through. It was also putting in processes and the professionalisation.
"A little bit of how we operated and what we did was a real challenge. There also needed to be a look at what's next.
"It was almost like what one environment wasn't able to give, the other one was in a position to. It just felt like the right time [to join Newcastle]."
Oxtoby talks fondly about her time with Northern Ireland but admitted "not everything was perfect".
Changes were needed to speed up their growth to help them break into League A of the Nations League and back to a major tournament.
"I came from a club environment where you're around people every day, to then going into an international environment where you're quite isolated at times," said Oxtoby.
"It was the ability from a staffing structure for us to have in place what we needed and we were building towards that, but it was probably not going quickly enough.
"It's just one of those things. When I look at the number of staff we've got [at Newcastle] to be able to bring processes to life, I felt when I went into Northern Ireland there probably wasn't that.
"It's something they are still working towards. The support I got and the willingness to make it better - all of that was there. But it just felt like it was taking a little bit longer than I would have liked."