Heat the olive oil in a large pot over medium heat.
Add the sausage and cook until browned, about 5-7 minutes.
Remove the sausage from the pot and set aside.
Add the onion and bell peppers to the pot, sautéing for about 5 minutes until softened.
Stir in the garlic and cook for an additional minute until fragrant.
Return the browned sausage to the pot and add the diced tomatoes and Italian seasoning.
Season with salt and pepper, bringing the mixture to a simmer.
Cover the pot and simmer on low heat for 15-20 minutes.