Preheat the oven to 400 degrees F (200 degrees C). Grease cookie sheets.

Mix together whole wheat flour, all-purpose flour, cornmeal, and oats. Make a well in the center of the dry ingredients and gradually pour in water, oil, eggs, peanut butter, and vanilla. Mix well.

On a flat surface, use a rolling pin to roll out the dough. Cut the dough into dog biscuit shapes using a cookie cutter. Place the biscuits onto the prepared cookie sheets.

Bake the biscuits in the preheated oven for 20 minutes. After 20 minutes, turn off the oven but let the biscuits remain inside the oven for another 20 minutes to harden.