Coat a large nonstick skillet with cooking spray, heat over medium high heat. Add onion and garlic to skillet and saute until slightly softened, about 2 to 3 minutes.
Meanwhile, place rice, broth, tomato puree, beans, bacon, chipotle sauce, oregano, salt and pepper in a 3 to 4 quart slow cooker, add sauteed vegetables. Cover and cook on low setting for 3 1/2 hours. Stir in cilantro and scallions just before serving.