Easy Italian Sausage Spaghetti

Heat olive oil in a large skillet over medium-high heat. Cook and stir sausage, mushrooms, onion, green bell pepper, and garlic in hot oil until sausage is browned and crumbly, about 20 minutes; drain and discard grease.

Stir tomato sauce, diced tomatoes, tomato paste, and olives into sausage mixture; season with oregano, basil, and salt. Simmer mixture until flavors infuse, about 30 minutes.

Meanwhile, bring a large pot of lightly salted water to a boil. Cook spaghetti in boiling water, stirring occasionally, until tender yet firm to the bite, about 12 minutes. Drain.