1. Remove coarse stems and discolored spots from greens; coarsely chop greens, and set aside.
2. Coat a large Dutch oven with cooking spray. Add oil, and place over medium-high heat until hot. Add onion; cook, stirring constantly, until tender. Add greens, broth, and remaining ingredients. Bring to a boil over medium-high heat. Cover and reduce heat; simmer 1 hour or until tender.