Arrange kale and cabbage in a vegetable steamer. Steam, covered, 8 to 10 minutes or until tender. Drain.
Meanwhile, heat oil in a nonstick skillet over medium heat. Place bacon in pan and cook until crisp. Remove bacon from pan; crumble. Add onion to drippings in pan; sauté 4 minutes. Add kale and cabbage, and cook until thoroughly heated. Stir in crumbled bacon. Sprinkle with salt and pepper.