Add olive oil to a large skillet over high heat. Season stew meat with salt and pepper and sear on all sides.
Place in a 4-quart slow cooker. Add onion, green chiles, and bacon. Add seared stew meat.
In a small bowl, whisk together tomato puree, Mexican seasoning, chili powder, salt and pepper and beef stock. Pour into slow cooker.
Cover and cook on HIGH setting for 4 to 6 hours. Serve in bowls garnished with scallion