Coat a large saucepan with cooking spray. Add onion; cook and stir over medium heat for 4 minutes or until tender. Add 4 cups corn; cook and stir until corn is softened, about 5 minutes. Add 2 cups broth; bring to a boil. Reduce heat; cover and simmer for 10 minutes or until corn is tender. Cool slightly.
In a blender, process soup in batches until smooth; return all to the pan. Add the red pepper, rosemary, thyme, pepper, cayenne and remaining corn and broth; cook and stir for 10 minutes or until the corn is tender.