Put lentils in a small saucepan with 2 cups water and bring to a boil over high heat. Cover and simmer until lentils are very tender, about 40 minutes. Drain well and set aside.

Put bulgur in a small saucepan with 1 1/2 cups water and bring to a boil over high heat. Cover and simmer until bulgur is tender and water is absorbed, about 15 minutes. Set aside.

In a medium skillet, combine mushrooms, onion, cider poultry seasoning and salt. Cover and simmer over medium heat until vegetables are very tender, about 15 minutes. Transfer to a food processor and pulse until finely chopped. Scrape into a bowl and fold in lentils, bulgur, oats, bell pepper and parsley.

Preheat oven to 375°F. Line the bottom and sides of an 8- or 9-inch loaf pan with parchment paper. Pack lentil mixture firmly into pan and smooth the top. Bake until edges brown slightly, about 1 hour. Cool in pan 25 minutes, then invert it onto a serving plate. Remove parchment and let the loaf cool a few more minutes. Use a serrated knife to cut the loaf into 1-inch-thick slices.

To freeze leftovers, let the loaf cool to room temperature, cut into serving slices, wrap in foil or freezer-safe plastic wrap and freeze up to 1 month.To reheat, unwrap and microwave, or place on a parchment-lined baking sheet and bake in a 275°F oven until heated through, about 45 minutes.