My brother begs for these every single weekend. Only 3 ingredients to prep, wrap them up, and let them cook until they are melt-in-your-mouth tender.

This slow cooker 3-ingredient steak fajita packets recipe is what I turn to when I want something that tastes like I fussed, but took almost no effort. You prep just three ingredients, wrap them in foil, and let the slow cooker do the work until the steak is melt-in-your-mouth tender. Fajitas, in their Tex-Mex form, grew popular along the Texas–Mexico border, traditionally made with marinated skirt steak cooked quickly over high heat. Here, we borrow those familiar flavors—beef, peppers, and onions—but adapt them to a low-and-slow, weeknight-friendly method that my family (especially my brother) asks for every single weekend.

Serve the steak fajita packets right in their foil, letting everyone open their own bundle at the table. Offer warm flour or corn tortillas, lime wedges, and a simple side like black beans, cilantro-lime rice, or a crunchy green salad. If you like, put out a small tray of toppings—shredded cheese, sour cream, salsa, and avocado—so people can customize without adding any extra work during prep. A light Mexican-style lager or sparkling water with lime rounds out the meal nicely.

Slow Cooker 3-Ingredient Steak Fajita Packets

Servings: 4

Ingredients

2 pounds beef flank steak or skirt steak, sliced into 1/2-inch thick strips
3 large bell peppers (mixed colors if possible), cored and sliced into 1/2-inch strips
2 large yellow or red onions, peeled and sliced into 1/2-inch thick strips

Directions

Prepare the slow cooker and foil: Line up 6–8 pieces of heavy-duty aluminum foil on your counter, each about 12 inches long. Lightly crimp the edges upward to create shallow trays so juices don’t escape while you’re filling them. Set your slow cooker base nearby with the insert in place.

Slice the steak: Place the flank or skirt steak on a cutting board and slice it across the grain into 1/2-inch thick strips. Cutting across the grain is important for tenderness, especially with these leaner cuts that will cook for several hours.

Slice the vegetables: Core and seed the bell peppers, then slice them into 1/2-inch wide strips. Peel the onions, halve them from root to tip, and slice into 1/2-inch thick slices so they cook at the same rate as the peppers and don’t disappear into mush.

Assemble the packets: Divide the sliced peppers and onions evenly among the foil sheets, creating a bed of vegetables in the center of each. Top each pile of vegetables with a portion of sliced steak, spreading it out so it’s in a relatively even layer rather than one tall mound. This helps everything cook evenly and become tender.

Seal the packets: Bring the long sides of each foil sheet up and over the steak and vegetables, then fold them together tightly to seal. Fold up the short ends as well, crimping firmly so the packets are well sealed but not compressed flat. You want a bit of space inside for steam to build, which helps the meat become very tender.

Load the slow cooker: Arrange the foil packets snugly in a single layer inside the slow cooker insert, seam side up. It’s fine if they’re touching and slightly overlapping, as shown in many home-style slow cooker photos—the packets will still cook evenly.

Cook low and slow: Cover the slow cooker with its lid. Cook on LOW for 6–8 hours, or until the steak is very tender and the peppers and onions are soft and sweet. Avoid opening the lid during the first few hours so you don’t lose heat and extend the cooking time.

Check for doneness: After about 6 hours, carefully open one packet (watching for hot steam) and test a piece of steak with a fork. It should be easy to pull apart and taste well-seasoned from the concentrated juices of the peppers and onions. If it still feels a bit firm, reseal the packet and continue cooking for another 1–2 hours.

Serve the packets: When the steak is melt-in-your-mouth tender, turn off the slow cooker. Use tongs to lift the packets onto plates or a serving platter. Let everyone open their own packet at the table, spooning the juicy steak, peppers, and onions into warm tortillas or over rice. Pour any flavorful juices from the foil over the filling for extra moisture and richness.


Variations & Tips

Because this recipe leans on just three ingredients, small tweaks can make a noticeable difference. For a deeper, more classic fajita flavor without adding extra prep ingredients, use a more intensely flavored onion, like red onion, and choose at least one red bell pepper for sweetness. If your household is comfortable with a tiny bit of extra work beyond the core three ingredients, you can sprinkle a ready-made fajita or taco seasoning blend over the steak before sealing the packets—no chopping, just a quick shake from the jar. To keep things strictly three-ingredient but boost savoriness, choose a fattier cut like well-marbled chuck steak, sliced thin; it will become incredibly tender and almost shreddable. You can also adapt the method for chicken by swapping in boneless skinless chicken thighs, sliced into strips, and cooking on LOW for about 4–5 hours. For a lower-carb approach, skip tortillas and serve the contents of each packet over cauliflower rice or a bed of shredded lettuce. Leftovers reheat well in a skillet over medium heat; let the juices reduce slightly to intensify the flavor and pile the mixture onto toasted rolls for an easy fajita-style sandwich.