Preheat your oven to 350°F and lightly grease a 9 x 13 x 2-inch baking dish with nonstick spray.

In a large skillet over medium-high heat, cook the ground beef until it’s fully browned, breaking it apart as it cooks. Season with salt and pepper.

Add the diced onion and both red and green bell peppers to the skillet and sauté for a few minutes, until the onion is soft and translucent. Once done, drain off any excess fat and remove the skillet from the heat.

While the meat is cooking, peel the russet potatoes and slice them thinly. Place the slices in a large bowl of cold water to keep them from browning.

In a separate medium bowl, whisk together the evaporated milk, cream of mushroom soup, and cream of chicken soup until smooth.

Drain the sliced potatoes and pat them dry using clean paper towels. Arrange half of the potatoes in an even layer across the bottom of the prepared baking dish.

Spoon half of the beef and vegetable mixture over the potatoes, then pour over half of the soup mixture. Sprinkle 1½ cups of shredded cheddar cheese on top.

Repeat the layers with the remaining potatoes, meat mixture, soup mixture, and top with the remaining 1½ cups of cheddar cheese.

Finish by sprinkling the crispy fried onions over the top, then cover the baking dish tightly with aluminum foil.

Bake in the preheated oven for 75 to 80 minutes, or until the potatoes are tender and the casserole reaches an internal temperature of 165°F. Remove the foil and broil on high for 1 to 2 minutes until the top is nicely golden and crisp.

Allow the casserole to rest for about 10 minutes before serving so the potatoes can absorb any remaining liquid and the layers can set properly.