1. Heat a large nonstick skillet over medium-high heat. Add onion to pan; sauté 5 minutes or until tender. Remove from heat.
2. Place onion in a 2 1/2-quart electric slow cooker coated with cooking spray. Add cheese and next 5 ingredients (through cream cheese). Stir until blended. Cover and cook on LOW for 1 1/2 hours or until cheese melts, stirring after 45 minutes. Top with green onions and bacon.