Great question! Grass-fed meat has much less fat (marbling) whether it's beef or lamb. I recently taught a class on cooking with grass-fed beef and some of the recommendations I made were: (1) Marinate the meat in a oil-based marinade for at least 1 hour, preferably overnight; (2) Cook it over lower heat than you would with grain-finished meat. The lower fat levels allows the meat to cook much faster. (3) For steak cuts, never grill, broil or pay-fry it beyond medium-rare. If you like your meat medium, don't get steaks - they will always be tough at medium or beyond. In that case, go with a braising cut like the shoulder. (4) Braising grass-fed meats work great because you're cooking it in a liquid. (5) Back to steak cuts, I highly prefer grass-fed meat that's been aged longer than normal. If you can get 4-6 weeks aging on the beef, it makes a huge difference in the tenderness. For example many Whole Foods stores will do additional aging once the meat comes in to them. It's more expensive, but makes an unbelievable difference. And (6) the last point on the steak cuts is to go for a cut that naturally has a higher fat level due to the type of cut, like a rib-eye. It'll still be a lot less fatty than grain-finished, but will have more fat than a NY Steak and so will be more flavorful and tender in the grass-fed version. Is it worth all this trouble? Yes. It's a much better (more humane) way to raise the animal (in theory, at least) and ends up with a much healthier cut of beef. Omega 3 is the fat in grass, so when you have a grass fed animal, the meat will have much more Omega 3 fats in it than grain-finished. This might be MUCH more information than you were looking for, but I hope some of it will be helpful. Don't give up on the grass-fed meats!

If by beef you mean steaks I'm thinking that it doesn't have enough marbeling although it does still have a pleasing flavor. Braising it as opposed to grilling will help.

Grass fed, in a general way, tends to have less fat and cooks a little faster.

What cuts have you purchased and how have you cooked them?

http://www.americangrassfed.org/wp-content/uploads/Tips%20for%20Cooking%20Grassfed%20Meats.pdf