Heat oil in large skillet over medium-high heat until hot. Sprinkle steak with salt and pepper. Place steak in skillet; cook 4 to 6 minutes or until well browned, turning once.
Transfer steak to 4 to 6-quart slow cooker. Top with onion and bell pepper. In same skillet, combine soup and salsa; mix well. Pour over vegetables and steak.
Cover; cook on low setting for 8 to 10 hours.
Remove steak pieces from slow cooker; place on serving platter. Stir sauce well. Serve sauce with steak.