Preheat oven to 350 degrees F. Coat a 3-quart rectangular baking dish with cooking spray; set aside. Cook bison sausage and onion over medium heat in an extra-large skillet until bison sausage is brown. Add apple and cook for 5 more minutes. Drain off fat.
Whisk eggs, milk, sage, and pepper in a large bowl.
Place bread cubes in prepared baking dish. Top with bison sausage mixture and the cheese. Gently mix to evenly distribute ingredients. Pour egg mixture over bread mixture.
Bake, uncovered, for 40 to 45 minutes or until a knife inserted near the center comes out clean. Let stand for 10 minutes before serving.
Make Ahead Tip: Prepare as directed through Step 3. Cover and chill for up to 48 hours. Preheat oven to 350 degrees F. Bake uncovered for 50 to 55 minutes or until a knife inserted near the center comes out clean.
Note: Recipe developed and tested by the Better Homes and Gardens(R) Test Kitchen using High Plains Bison products.