Info from US Wellness Meats:
U.S. Wellness Meats — Our Animals Eat Right So You Can Too.
In my own area there are two ranches. One sells grass-fed beef. They grow the grass. They use irrigation. They use chickens for fertilizer for the grass. The other ranch grazes the animals on the native grasses and supplements with barley, oats and hay.
Personally I would not worry one single bit whether the grasses and supplemental feed were certified organic. It's highly unlikely anyone would ever certify animal feed anyway.
Female, 5'3", 48, Starting weight: 163lbs. Current weight: 135.
Starting squat: 45lbs. Current squat: 145 x 4.