Step 1

Preheat the oven to 375 degrees F.

Step 2

Coat a 9x13-inch baking dish with nonstick cooking spray.

Step 3

In a large, nonstick pan over medium-high heat, add 1 tablespoon of the olive oil.

Step 4

Add the mushrooms to the hot oil and cook, while stirring, until the mushrooms release their liquids, the liquids have evaporated, and the mushrooms are lightly browned, about 5 minutes.

Step 5

Transfer the mushrooms to the bottom of the prepared baking dish, spreading them out evenly.

Step 6

In a separate, large, nonstick pan over medium-high heat, add 1 tablespoon of the remaining olive oil.

Step 7

Add the sausages to the hot oil and cook, while turning the sausages occasionally, until they are browned on all sides, about 2-3 minutes per side.

Step 8

Transfer the sausages to a cutting board and allow them to cool slightly.

Step 9

Slice the sausages in half lengthwise, then cut the sausages into thick half-moons.

Step 10

Return the sausage pieces to the pan over medium-high heat and cook, while stirring them occasionally, until the cut sides of the sausages are browned and the sausage pieces reach an internal temperature of 145 degrees F, about 2 minutes per side.

Step 11

Transfer the sausage pieces to a plate and set them aside.

Step 12

In the same pan used to cook the mushrooms, over medium-high heat, add the remaining olive oil.

Step 13

Add the red bell peppers and the green bell peppers to the hot oil and cook, while stirring, until they just begin to soften, about 4 minutes.

Step 14

Add the pepper mixture over the mushrooms in the baking dish.

Step 15

Season the mushrooms and the pepper mixture in the baking dish with the Italian herb blend, the all-purpose seasoning, and the black pepper

Step 16

Layer the sausage pieces over the pepper mixture in the baking dish.

Step 17

Sprinkle the sausage layer evenly with the mozzarella cheese.

Step 18

Bake until the casserole is sizzling hot and the cheese is melted and browned, about 25 minutes.

Step 19

Serve hot.