Heat a 12-inch skillet over medium heat. After the skillet gets hot, add the cooking oil and sausage links.
2 tablespoons cooking oil, 5 Italian sausage links
Cook the sausage for 5-6 minutes on each side until the casings are nicely browned. Remove the sausages to a waiting plate, and leave the drippings in the pan.
Add the bell peppers and onion to the same pan used to cook the sausage. Cook over low heat until they begin to soften (about 3-5 minutes), then add the garlic.
1 green bell pepper, 1 yellow bell pepper, 1 red bell pepper, 1 medium white onion, 3 garlic cloves
Cook an additional 30 seconds, then add the tomatoes, Italian seasoning, salt, and pepper. Stir to combine.
15 ounces diced tomatoes, 1 tablespoon Italian seasoning, Salt and pepper
Add the sausage links back to the pan. Simmer over low heat for 10-15 minutes to ensure the sausage is thoroughly cooked.
Serve hot in buns or slice the sausage into pieces and serve over pasta or rice.