Yes it is possible to feed lambs without grain and and a 100 % “from the land”. For that you need to have good electric fences and move them very often. That way they get all the nutrition they need from forbs, forage and grass (grass alone would not do it). And their meat is healthier for you because of the omega 3 and omega 6 fats. The very moment you start feeding grains to ruminants (cattle, sheep, goats) you start to reverse the omega 3 to 6 ratio to the bad side and after 4 weeks of feeding grains all the benefits of the forage are gone.
For our grazing and handling methods we got the AWA certification for grassfed lamb and grassfed beef. And we are working on our fences and handlings facilities for the pigs to achieve the same with them.
Only very few ranches in BC have the setup to achieve this. And by the way: Our meat tested at the top at Thompson Rivers University for CLA and omega 3 to 6 ratio.