Remove casings from sausage; crumble into 1-inch pieces. Heat a large saute pan over medium heat. Add the sausage; cook, stirring often, until browned and cooked through, about 8 minutes. Remove the sausage from the saute pan with a slotted spoon; set aside.Advertisement
Pour off all but 1 tablespoon of fat from the pan. Return to medium heat; add the onion. Saute the onion until it is just beginning to brown and soften, about 5 minutes. Add the peppers; continue to cook for 10 minutes more.
Add salt and pepper. Add tomatoes; bring to a boil, and then lower to a simmer until vegetables are tender and the sauce has reduced and thickened slightly, about 12 minutes more.
Return sausage to pan; cook just enough to heat through. Stir in parsley; adjust seasoning with salt and pepper.