Spray 1 1/2-quart slow cooker with cooking spray. In 10-inch skillet, heat oil over medium-high heat. Add beef; cook 4 to 5 minutes or until browned on both sides. Sprinkle both sides of steak with 1 tablespoon of the taco seasoning mix.
In small bowl, mix remaining 1 tablespoon taco seasoning mix with remaining ingredients. Place 1 steak in bottom of slow cooker. Cover with half of the salsa mixture. Repeat with remaining steak and salsa mixture.
Cover; cook on Low heat setting 8 to 9 hours.