I didn’t attend OCS but I did graduate from NCOLS (NCO Leadership School) as a young Corporal in 1987. It was at Quantico and was operated by OCS and TBS Drill Instructors. I was stationed at Marine Barracks in DC so the nearest NCOLS was in Quantico.
If memory serves, the Quigley is located in the woods to the west in the map you posted. If you start at the Parade Ground and move west you will see the obstacle course just across a grassy field. Immediately to the west of the obstacle course beyond the treeline is where the Quigley begins.
It then snakes south-southwest around that swampy area turning north until you end up in the thicker woods. Beyond that is where all the obstacles are found which you cannot see in the photo because of the tree cover.
The final stretch (where you belly crawl through mud and water (THE “Quigley”)) ends up somewhere near the orginal starting point.
As I said, this was 25 years ago so it may have changed since then, although I will never forget that experience. As NCOs going through NCOLS it was a priviledge to be able to tackle something that officers usually only get to do.
It appears things have changed a bit since then as I see the barracks in which we were housed for NCOLS just north of the Parade Ground are gone and replaced with other buildings.
Hope this is helpful. Any Marine officers out there feel free to correct me if I’ve given bum or outdated information.
That worked. Zooming in you can see elements of obstacles in the water, pole structures for rope climbing, etc. Tree cover is thick, but you can discern many small structures.