Grass fed or pasture-raised meat is cooked differently than factory produced, grain fed industrial meat. For example, grass fed meat is leaner than grain fed so it doesn't have a lot of extra fat. This means you must take a little extra care when cooking grass fed meats.
Wondering what exactly grass-fed, pasture-raised meat is? 1
Truly sustainable livestock farming requires the use of a pasture-based system. Pasture-raised animals roam freely in their natural environment where they're able to eat nutritious grasses and other plants that their bodies are adapted to digest. In addition to dramatically improving the welfare of farm animals, pasturing also helps reduce environmental damage, and yields meat, eggs, and dairy products that are tastier and more nutritious than foods produced on factory farms.
The number one rule for cooking pastured meat is not to overcook it. It needs about 30 percent less cooking time than most common beef and is best if cooked medium-rare to medium. Otherwise, it might be too tough. Overcooking is the number one problem most people have when they switch to pastured meat, so don't give up if it takes you a couple tries before you master cooking pastured products.
If you're cooking hamburgers made with pasture raised beef, add caramelized onions or other moisturizing ingredients to compensate for the leaner meat. (Grass-fed hamburgers are generally 80 to 90% lean)
1- Parphrased text from The Sustainable Table