Heat oil in large saucepan. Add onion; cook, stirring occasionally, until tender. Add 4 cups corn; cook, stirring occasionally, until tender. Add water and bouillon; cook, stirring frequently, for 15 minutes or until corn is very soft.
Place corn mixture in blender or food processor; blend until smooth. Return to saucepan. Stir in remaining corn, evaporated milk, bell pepper and rosemary. Cook, stirring frequently, for 10 minutes or until chowder is thick and bell pepper is tender. Season with salt and ground black pepper, if desired. Garnish with rosemary.
Note: For a Southwestern-style twist to this recipe, add 1 can (4 ounces) diced green chiles with the bell pepper. Eliminate rosemary; stir in 1 teaspoon chopped fresh cilantro. Garnish with cilantro leaves instead of rosemary.