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Slow Cooker Beef Stir Fry

by Katerina Petrovska

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Updated Sep 27, 2026

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This Slow Cooker Beef Stir Fry features tender flank steak, bell peppers, and onions simmered in a sweet, savory sesame-soy sauce. Serve it over rice for an easy, flavor-packed dinner.

This slow cooker beef stir fry recipe started as one of those clean-out-the-fridge dinners. I had flank steak, an onion, a couple of forgotten bell peppers, and rice in the pantry, so I put everything to work. These days, I make it with a simple homemade sesame-soy sauce, and it’s become such an easy way to turn flank steak and a few vegetables into dinner.

I give the flank steak a quick sear first, then let it cook low and slow with onions, garlic, ginger, and that sweet and savory sauce. The bell peppers go in toward the end so they don’t turn to mush, and a quick cornstarch slurry thickens up the sauce before serving. Spoon everything over hot rice, and dinner is done.

Why You’ll Love My Slow Cooker Beef Stir Fry

• Mostly hands-off. Sear the beef, sauté the aromatics, and let the slow cooker take it from there.
• Homemade stir fry sauce. Soy sauce, honey, rice vinegar, sesame oil, and ginger make a sweet and savory sauce without anything bottled.
• A different way to cook flank steak. It slow cooks whole until tender, then gets thinly sliced and tossed back into the sauce.
• Easy to customize. Add broccoli, snap peas, mushrooms, or carrots along with the bell peppers.

Recipe Ingredients

• Flank steak: Keep it whole while it slow cooks, then slice it thinly against the grain before returning it to the sauce.
• Bell peppers: Add them during the last hour of cooking to keep them from becoming too soft.
• Onion and garlic: I cook these briefly in the same skillet used to sear the beef. A splash of beef broth loosens up all those browned bits from the bottom of the pan.
• Ginger: Just ½ teaspoon of ground ginger or a teaspoon of freshly grated ginger adds plenty of warm flavor to the sauce.
• Low-sodium soy sauce: Definitely go with low-sodium here since we’re using ½ cup.
• Honey: Adds sweetness and helps give the finished sauce that glossy, sticky texture.
• Rice vinegar: Balances the sweetness of the honey and the saltiness of the soy sauce.
• Sesame oil: A little goes a long way and gives the sauce its sesame flavor.
• Cornstarch: Mix it with cold water and stir it in at the end to thicken the cooking liquid into a sauce.

How to Make Beef Stir Fry in the Slow Cooker

• Start by searing the flank steak in a hot skillet. This only takes a few minutes, but that browning adds a lot of flavor. Transfer the steak to your slow cooker, then use the same skillet to soften the onion and quickly cook the garlic and ginger. Deglaze the pan with beef broth and pour everything over the steak.
• Whisk together the soy sauce, honey, rice vinegar, and sesame oil and pour the sauce into the slow cooker. Cook until the flank steak is tender, adding the bell peppers during the last 45 to 60 minutes.
• Once the beef is done, let it rest briefly before slicing it thinly against the grain. Return the sliced beef to the slow cooker, stir in the cornstarch slurry, and let the sauce thicken for another 10 to 15 minutes.

Serving Suggestions

This jasmine rice recipe is my go-to with this beef stir fry because it soaks up all that sesame-soy sauce, but brown rice or quinoa work great, too. On the side, add my sesame cucumber salad for something cool and crunchy, or try my Asian cucumber salad if you want a little more heat.

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Slow Cooker Beef Stir Fry

by Katerina Petrovska

This slow cooker beef stir fry is made with tender flank steak, bell peppers, and onions cooked in a savory homemade sesame-soy sauce. It’s an easy, flavorful dinner that’s perfect served over rice.

Prep Time: 10 minutes minutes

Cook Time: 4 hours hours

Total Time: 4 hours hours 10 minutes minutes

Servings: 4

Ingredients 

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• ▢ 1 tablespoon vegetable oil, or canola oil
• ▢ 1½ to 2 pounds flank steak
• ▢ salt and freshly ground black pepper, to taste
• ▢ 1 large yellow onion, sliced
• ▢ 3 cloves garlic, minced
• ▢ 1 teaspoon freshly grated ginger, or ½ teaspoon ground ginger
• ▢ ¼ cup low sodium beef broth, or water
• ▢ ½ cup low-sodium soy sauce
• ▢ ¼ cup honey, or packed brown sugar
• ▢ 2 tablespoons rice vinegar
• ▢ 1 tablespoon toasted sesame oil
• ▢ 2 bell peppers, any color, cut into strips
• ▢ 1 tablespoon cornstarch
• ▢ 1 tablespoon cold water
• ▢ sliced green onions and sesame seeds, for garnish, optional

Instructions 

• Sear the beef. Season the flank steak with black pepper and a little salt. Heat 1 tablespoon of cooking oil in a large skillet over medium-high heat. Sear the steak for 1 to 2 minutes per side, just until browned. Transfer it to the slow cooker.
• Add the onion and garlic. In the same skillet, cook the onion, garlic, and ginger for 1 minute. Pour in the beef broth and scrape up the browned bits from the bottom of the skillet. Transfer everything to the slow cooker, spooning it around and over the steak.
• Make the sauce. Whisk together the soy sauce, honey, rice vinegar, and sesame oil. Pour the sauce over the beef.
• Slow cook. Cover and cook on LOW for 4 to 5 hours or on HIGH for 2½ to 3 hours, until the flank steak is tender.
• Add the peppers. Add the sliced bell peppers during the last 45 to 60 minutes of cooking so they become tender without getting overly soft.
• Slice the beef. When cooked, transfer the flank steak to a cutting board and let it rest for about 5 minutes. Thinly slice the steak against the grain, then return it to the slow cooker.
• Thicken the sauce. Whisk the cornstarch with 1 tablespoon of cold water until smooth. Stir the slurry into the slow cooker. Cover and cook on HIGH for another 10 to 15 minutes, or until the sauce has thickened.
• Serve. Stir everything together and serve over rice or quinoa, garnished with green onions and sesame seeds.

Equipment

• Slow Cooker

Notes

• Adjust the sauce. The beef and vegetables will release liquid as they cook. If you’d like more sauce at the end, stir in a splash of water or low-sodium beef broth before adding the cornstarch slurry.
• Don’t overcook the beef. Flank steak is lean, so start checking it at the earlier end of the cooking range. The beef is ready when it’s tender and slices easily; cooking it much longer can make it dry and stringy.
• Slice against the grain. Flank steak can be chewy if it’s sliced with the grain. Look for the long muscle fibers and cut across them into thin strips.

Nutrition

Serving: 1.5cups | Calories: 339kcal | Carbohydrates: 28g | Protein: 29g | Fat: 13g | Saturated Fat: 3g | Polyunsaturated Fat: 4g | Monounsaturated Fat: 4g | Trans Fat: 0.02g | Cholesterol: 68mg | Sodium: 1240mg | Potassium: 717mg | Fiber: 2g | Sugar: 21g | Vitamin A: 1864IU | Vitamin C: 79mg | Calcium: 50mg | Iron: 3mg

Nutritional info is an estimate and provided as courtesy. Values may vary according to the ingredients and tools used. Please use your preferred nutritional calculator for more detailed info.

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