"The different feeding practices are complicated and varied.
For example, grass-fed beef in Australia may not be directly comparable to US products, and grass-fed beef isn’t necessarily pasture-raised. Not all grass-fed cows can graze outdoors.
In fact, the term grass-fed isn’t clearly defined.
That said, grass-fed cows eat (mostly) grass, while grain-fed cows eat (mostly) an unnatural diet based on corn and soy during the latter part of their lives."
https://www.healthline.com/nutrition/grass-fed-vs-grain-fed-beef#grassfed-vs-grainfed
""Grass (Forage) Fed" means that grass and forage shall be the feed source consumed for the lifetime of the ruminant animal, with the exception of milk consumed prior to weaning. The diet shall be derived solely from forage consisting of grass (annual and perennial), forbs (e.g., legumes, Brassica), browse, or cereal grain crops in the vegetative (pre-grain) state. Animals cannot be fed grain or grain byproducts and must have continuous access to pasture during the growing season."
https://ask.usda.gov/s/article/What-is-grass-fed-meat
"The USDA Grass Fed Program for Small and Very Small (SVS) Producers was designed to create opportunities for small-scale livestock producers who would like to have their ruminant animals certified as grass fed. This program, is designed for producers who market 49 cattle or less each year or lambs produced from 99 ewes or less.
This program requires that ruminant animals be fed only grass and forage, with the exception of milk consumed prior to weaning."
https://www.ams.usda.gov/services/auditing/grass-fed-SVS