Grass fed vs Grain fedThe amount of land you have available to you will determine the answer to this question. If you have very little land, then you will need to grain finish your beef. This will be a combination of grass, hay, and grain.
If you have a fair amount of land, my guess is 25 acres or more you may be able to grass fatten your beef. You will need to check with your local experts. Start with your state extension agents.