Abstract: The presently disclosed subject matter is generally directed to a slow feeder grazing muzzle for use with animals, such as horses. Slow feeder grazing muzzles fit over at least a portion of the animal's nose and mouth, affecting the amount of grass or other feed that is accessible to the animal. The disclosed muzzle includes a top flap, bottom flap, and opposing side flaps that are capable of interconnecting with each other to form a central opening. In addition, a series of interchangeable inserts can be positioned within the central opening to adjust the amount of grass or feed the horse can access. In this way, the rate of speed and amount of grass the horse eats can be controlled and/or adjusted as desired by the owner.