The Swiss international played the opening 45-minutes as the young Magpies beat Crystal Palace under-23s 2-0 at Whitley Park.
Christian Atsu was also among the starters as goals from Adam Wilson and Kyle Crossley in either half saw the hosts claim three points.
It was the first time Schar had featured in a game since suffering a serious knee injury in the 3-2 win over Southampton back in early February.
After requiring surgery and spending 11 weeks on the sidelines, Schar returned to training last week.
And following his playing return on Monday, the Newcastle defender tweeted: “Good to get some min in the tank.. feels good to be back on the pitch.”
The 29-year-old’s contract at United expires in the summer though the club do have an option to extend his deal for another year.