Heat oil in a large cataplana or saucepan with lid over medium-high heat. Add sausage and cook, stirring occasionally, 5 minutes or until lightly browned.
Add onion, next 4 ingredients, and red pepper, if desired; cook 5 minutes or until vegetables are tender. Stir in tomatoes and wine; bring to a boil. Add clams and shrimp.
Lock cataplana lid and cook, shaking cataplana occasionally, 7 minutes or until clams open. Or, cover saucepan and cook, stirring occasionally if necessary, 7 minutes or until clams open. (Discard any that do not.) Open carefully; sprinkle with parsley.