Slow Cooker Mongolian Beef is sweet, savory, and tender with a glossy sauce that clings to thin slices of beef. The meat becomes melt-in-your-mouth soft while the sauce balances brown sugar and soy for deep caramel notes. Texture is silky thanks to a light cornstarch coating, and bright green onions added at the end give a fresh snap. This recipe is special because it’s mostly hands-off—toss, slow cook, and serve. For a simple weeknight meal, spoon it over steamed rice or cauliflower rice for a quick dinner that feels like takeout. If you like easy slow-cooker dinners, try this approach similar to Crock-Pot Angel Chicken for another no-fuss option.

Why You’ll Love This Slow Cooker Mongolian Beef

Hands-off cooking: toss everything in the slow cooker and let it finish itself.
Deep, caramelized flavor from brown sugar and soy—no stove-top browning needed.
Tender flank steak slices that stay moist and not stringy.
Quick to prep—about 10 minutes to coat and stir.
Flexible for serving: rice, noodles, or low-carb options all work.
Uses pantry staples you may already have.
Bright finish with green onions adds color and freshness.
Great for meal prep—reheats well and feeds a family.

What Is Slow Cooker Mongolian Beef?

Slow Cooker Mongolian Beef is a slow-cooked version of the classic Mongolian beef you find at restaurants. It features thinly sliced flank steak tossed in cornstarch, then cooked in a sweet-savory sauce of soy and brown sugar with sesame oil, garlic, and ginger. The slow cooker lets the sauce develop a deep, rounded flavor while the beef becomes very tender without constant stirring. The vibe is comforting and slightly upscale—perfect for weeknight dinners, casual gatherings, or when you want a simple takeout-style meal at home. It keeps the classic brightness and sweetness of Mongolian-style sauces but with the ease of set-and-forget cooking.

Ingredients for Slow Cooker Mongolian Beef

For the Base

1 1/2 pounds flank steak (thinly sliced against the grain)
1/4 cup cornstarch

For the Sauce

1 tablespoon toasted sesame oil
1 teaspoon minced garlic
1 teaspoon minced ginger
1/2 cup low sodium soy sauce
1/3 cup brown sugar
1/2 cup water

To Serve

1/2 cup green onions (for garnish)

Ingredient Notes (Substitutions, Healthy Swaps)

Flank steak: You can use skirt steak or sirloin tip if flank is not available—slice thin against the grain. These cuts keep texture similar.
Cornstarch: Arrowroot powder works as a 1:1 substitute for a more neutral flavor and clearer sauce. If you need a gluten-free option, use certified gluten-free cornstarch and gluten-free soy sauce.
Low sodium soy sauce: Essential to control salt. If you only have regular soy sauce, reduce added salt elsewhere and taste test at the end.
Brown sugar: For a slightly healthier swap, use coconut sugar 1:1 for a less sweet, slightly caramel flavor. Honey or maple syrup will change texture—use them as an optional variation.
Toasted sesame oil: Adds nutty aroma; if unavailable, use regular sesame oil or substitute with a neutral oil plus a small squeeze of sesame paste or tahini (optional and small amount).
Green onions: Scallions add freshness. If you don’t have them, thinly sliced chives or a light squeeze of lime can brighten the dish.

Step-by-Step Instructions

Step 1 – Coat the beef
Toss the thinly sliced flank steak with 1/4 cup cornstarch in a mixing bowl until each piece is evenly coated. Shake off any excess cornstarch so pieces are lightly dusted, not clumped.
Visual cue: The beef should look dry-matte with a fine white dusting, not clumpy or gummy.

Step 2 – Add to the slow cooker
Place the coated steak in a single layer in the slow cooker. It’s okay if pieces overlap; they will cook down.

Step 3 – Mix the sauce and pour
In a small bowl, whisk together 1 tablespoon toasted sesame oil, 1 teaspoon minced garlic, 1 teaspoon minced ginger, 1/2 cup low sodium soy sauce, 1/3 cup brown sugar, and 1/2 cup water. Pour the sauce over the beef and stir gently to combine so most pieces get coated.

Step 4 – Cook low and slow
Cover and cook on HIGH for 2–3 hours or LOW for 4–5 hours, until the beef is tender and the sauce is glossy.
Pro cue: On HIGH the edges may start to break down sooner—check at 2 hours for tenderness to avoid overcooking.

Step 5 – Finish with green onions
Stir in 1/2 cup green onions just before serving to add a fresh crunch and color.

Step 6 – Serve
Spoon the Mongolian beef over steamed rice, noodles, or a bed of greens. Serve immediately while hot.

Pro Tips for Success

Slice against the grain: This shortens the muscle fibers for more tender bites.
Thin, even slices cook more uniformly—partially freezing the steak for 15–20 minutes makes slicing easier.
Don’t overload the slow cooker: keep a single layer or light overlap for even cooking. If your slow cooker is small, cook in two batches.
Avoid lifting the lid: each time you lift the lid you lengthen cooking time and cool the slow cooker. Only check once near the shorter end of the cooking window.
Stir gently after cooking: too much stirring can break the beef into pieces. Fold to coat.
Taste before serving: because soy sauce and brown sugar can change with brands, taste and adjust by adding a pinch of sugar, splash of soy sauce, or a dash of water to balance.

Flavor Variations

Optional: Spicy kick — add 1–2 teaspoons chili garlic sauce or 1/2 teaspoon red pepper flakes to the sauce.
Optional: Sticky glaze — for a thicker sauce, remove the lid in the last 20–30 minutes and cook on HIGH to reduce, or mix 1 tablespoon cornstarch with 2 tablespoons cold water and stir in at the end, cook 15–20 minutes until thickened.
Optional: Citrus brightness — stir in 1 tablespoon rice vinegar or a squeeze of lime juice at the end to brighten flavors.
Optional: Veggie boost — add sliced bell peppers or snap peas in the last 30–45 minutes of cooking to keep them crisp.
Optional: Low-sugar — reduce brown sugar to 1/4 cup and add 1–2 tablespoons of a sugar-free sweetener like erythritol to taste.
Optional: Umami boost — stir in 1 teaspoon hoisin or a small pinch of fish sauce at the end for depth, used sparingly.

Serving Suggestions

Classic: Serve over steamed white or brown rice with a sprinkle of sesame seeds and extra green onions.
Low-carb: Spoon over cauliflower rice or steamed broccoli for a lighter plate.
Noodles: Toss with cooked lo mein or rice noodles for a saucy noodle bowl.
Family-style: Serve from the slow cooker on the table with bowls of rice and extra scallions for a casual dinner.
Plate it up: Arrange thinly sliced beef over a shallow bowl of rice, drizzle extra sauce, and top with green onions.
Party idea: Serve alongside steamed veggies and let guests build their own bowls.

Make-Ahead, Storage & Reheating

Make-ahead: Slice the beef and coat with cornstarch up to 24 hours in advance; store covered in the fridge. Sauce can be mixed ahead and refrigerated. Combine and cook when ready.
Refrigerator storage: Store leftovers in an airtight container for 3–4 days. The sauce will deepen in flavor after sitting.
Reheating: Reheat gently on the stove over low-medium heat, stirring occasionally until warmed through. Add a splash of water or broth if the sauce has thickened too much. For microwave, heat in 1-minute bursts, stirring in between.
Texture note: The beef may firm slightly after refrigeration; reheating slowly will help return softness. If sauce thickens, loosen with a little warm water.

Storage and Freezing Instructions

Freezing: You can freeze cooked Mongolian beef in airtight freezer-safe containers for up to 2 months. Portion into meal-sized containers and cool completely before freezing.
Thawing: Thaw overnight in the refrigerator before reheating. Reheat gently on the stove to restore texture.
If you prefer not to freeze the cooked dish: Freeze the raw sliced, cornstarch-coated beef and the sauce separately in freezer bags. Thaw and combine before cooking for better texture.
Note: Freezing can change the texture of cooked beef slightly; freezing raw-sauced components separately often gives a fresher result.

Nutrition Facts (Per Serving)

Calories | Protein | Carbs | Fat | Fiber | Sodium
480 | 36 g | 31 g | 23 g | 1 g | 1500 mg

Estimates vary by brands and portions.

FAQ About Slow Cooker Mongolian Beef

Q: Why is my sauce too thin?
A: The sauce thins if there’s excess water or if cornstarch is diluted. To thicken, mix 1 tablespoon cornstarch with 2 tablespoons cold water and stir into the slow cooker, then cook on HIGH for 15–20 minutes.
Q: Why is the beef tough?
A: Tough beef usually means it was slightly overcooked or sliced too thick. Slice against the grain and check for tenderness at the lower end of the time range.
Q: Can I use frozen steak?
A: It’s better to thaw before slicing and coating. Frozen steak is hard to thin-slice and can steam instead of browning in the slow cooker.
Q: How can I reduce the sodium?
A: Use low sodium soy sauce (as in the recipe) and reduce to 1/3 cup if needed. Taste and adjust with a small splash of water or a pinch of sugar.
Q: Can I double the recipe?
A: Yes, but use a larger slow cooker and keep meat in a shallow layer to ensure even cooking. You may need a little extra liquid.
Q: How do I get a glossy sauce?
A: Light cornstarch coating on the beef and the final stir release starch into the cooking liquid, creating a glossy finish. Avoid over-diluting with extra water.

TastyInspo Notes

Finish with raw green onions just before serving to keep their color and crunch.
For extra texture, top with toasted sesame seeds right before plating.
Warm your serving bowls to keep the beef hot longer.
If serving to kids, reduce ginger slightly and offer sauce on the side.
Use a wide slow cooker for a better single layer of meat and more even cooking.
When plating, spoon a little extra sauce over the rice first, then add beef for a restaurant-style look.

Troubleshooting

Bland flavor: Add a splash of soy sauce or a pinch more brown sugar, and finish with a squeeze of lime or dash of rice vinegar.
Too watery: Thicken with a cornstarch slurry (1 tbsp cornstarch + 2 tbsp cold water) and cook on HIGH for 15–20 minutes.
Overcooked, mushy beef: Next time reduce cook time or use the HIGH setting for a shorter period; check tenderness earlier.
Sauce too sweet: Add a splash of soy sauce or a little rice vinegar to balance the sweetness.
Not enough sauce: Add 1/4 cup water + 1 tablespoon soy sauce and cook 10–15 more minutes; cornstarch will help thicken if needed.
Oil separation: If the sauce separates after chilling, reheat gently and whisk to recombine; a brief simmer will emulsify.

Final Thoughts

This Slow Cooker Mongolian Beef delivers deep, takeout-style flavor with very little hands-on time. It’s forgiving, flexible, and great for busy nights or meal prep. The method highlights simple pantry ingredients to create a rich, glossy sauce and tender slices of flank steak that everyone will enjoy.

Conclusion

For another slow-cooker favorite and different flavor profile, check out this easy recipe for Slow Cooker Mongolian Beef recipe at Dinner at the Zoo.