My dogs love these, from Jerry Traunfeld's The Herbal Kitchen:

Makes 2-4 dozen.

1 1/2 cups rolled oats
2 cups whole wheat flour
1/4 cups dry nutritional yeast
1 1/2 tablespoon garlic powder
1 cup parsley sprigs, gently packed
1/2 cup peanut butter, preferably unsalted
1 egg
1 cup water

Preheat oven to 275 degrees F.

Whirl the oats, flour, yeast, garlic powder and parsley in a food processor until finely ground. Add the peanut butter and process until combined. Add the egg and water and process until dough forms a firm ball that spins around the blade.

Turn the dough out and knead briefly. Pinch off a piece of dough (large or small, depending on the size of your dog) and roll into a cylinder. Pinch in the middle to form a bone shape, pressing a fingertip into both ends to create sockets. Arrange biscuits on a parchment-lined baking sheet. Bake the biscuits for about 2 hours, or till lightly browned and quite dry. Cool and store in an airtight container out of paw's reach.