Fajita Nights Just Got a Whole Lot Easier with Slow Cooker Steak Fajitas! Fajita night at my house is all about sitting and relaxing with family, personalizing your own fajitas. Let the slow cooker do all the work while you put your feet up! This recipe will make sure your beef is tender and juicy with all that fajita flavor! All I do is open some salsa super quick with my handy jar opener and sit back with a Cerveza! Ingredients: 2 pounds flank steak 1-2 bell peppers, sliced 1 onion, sliced 20 ounces salsa 2 tablespoons fajita seasoning Directions: Add salsa to the bottom of the slow cooker. Add beef, onion, bell pepper, and fajita seasoning. Stir to mix well. Cook low 6-8 hour or high 3-4.