Preheat the oven to 350°F.

Place rolled oats in a food processor fitted with the metal blade and grind into a flour. Transfer oat flour into a large bowl.

Drain the sardines and add them to the empty food processor, add pumpkin, peanut butter, and egg, process until well-mixed.

Add 3 cups of oat flour to the wet ingredients mixture, one cup at a time and process each time until the flour is incorporated.

If the dough is still wet, sprinkle a little bit more of the reserved oat flour and process until the dough resembles pie dough.

Scrape the dough out onto an oat-floured countertop, shape into a ball and roll it out to about ¼" thick. Use the rest of the oat flour for rolling as needed to keep the dough from sticking to the counter and your rolling pin.

Cut with a cookie cutter if desired, or simply cut into squares with a knife. Place the treats on a baking sheet about ½” apart, and bake for 35 minutes. Flipping the treats over and rotating the baking pan about halfway through so they brown evenly.