The OATS walk was an annual challenge walk across Dartmoor over 2 days from Ivybridge to Postbridge and Postbridge to
Okehampton. Both days are 12 miles and mainly good walking over high moorland. The difficulty is getting back to the start
if you leave your car there.
The OATS walk was actually a one day walk from New Waste just outside Ivybridge via check points (if I remember rightly) at Postbridge and Quintins Man and last check in time in Okehamptonat 5pm. I did it in 2000 and my certificate has it as 27.5 miles, though as you made your own route between checks that wouldn't be precise. It was on 16 April and there was still snow in the gullies and peat passes.
The last OATS walk was in 2004.
Glad you both enjoyed your first experience of Dartmoor. No doubt there will be more to come.