Spray a baking dish with cooking oil and then add the sausage links in a single layer.
Combine the bell pepper, onion, garlic, olive oil, Italian seasoning, salt, and black pepper in a large bowl and toss until all of the ingredients are evenly coated with the oil and seasonings.
Transfer the vegetable mixture to the baking dish with the sausages and spread out into an even layer.
Bake for 35-40 minutes, flipping the sausages halfway through. Be sure to bake until the sausages are browned and cooked through (internal temperature of 160°F for pork or 165°F for chicken).