Slow Cooker Mongolian Beef (Easy & Freezer-Friendly)
Tender, Saucy Slow Cooker Mongolian Beef (Better Than Takeout)
If you love a cozy, takeout-style dinner that practically cooks itself, this slow cooker Mongolian beef is the one to keep on repeat. Think ultra-tender slices of beef in a glossy garlic-ginger soy sauce—sweet-savory, a little sticky, and absolutely weeknight-friendly. I reach for this recipe on the busiest days: when we’re running from school to activities, I just pull a kit from the freezer in the morning, drop it into the crock, and dinner rewards us with that irresistible “What smells so good?” moment.
We keep the ingredients simple (the way real families cook), build flavor with soy, garlic, and ginger, and finish with a quick cornstarch slurry so the sauce clings to every bite. You can batch a few kits at once—one for tonight and one (or two) for later. Serve over rice or noodles with a shower of green onions and sesame seeds and watch plates come back clean.
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What you’ll find in this Mongolian Beef guide
Ingredients for the Best Flavor (and Why They Work)
Just pantry staples, balanced for that classic Mongolian-beef taste:
2 lbs flank steak or sirloin , thinly sliced against the grain — flank gives tender chew; sirloin is budget-friendly and very tender when slow cooked.1/2 cup low-sodium soy sauce (or tamari) — the umami backbone; low-sodium keeps it from tasting overly salty after reduction.1/2 cup water or low-sodium beef broth — stretches the sauce and adds savory depth.1/3–1/2 cup brown sugar — classic Mongolian sweetness; start lower and adjust to taste. The sugar also helps the sauce lacquer.4 cloves garlic, minced + 1–2 Tbsp fresh ginger, grated — essential aroma and warmth (use 1 tsp ground ginger if needed).2 Tbsp rice vinegar (optional) — brightens the sauce so it’s not one-note sweet.1–2 tsp toasted sesame oil (optional) — a finishing aroma that screams “takeout night.”1/2 tsp red pepper flakes (optional) — a little heat to balance the sweet.4 Tbsp cornstarch, divided — 2 Tbsp for dusting beef (helps sauce cling), 2 Tbsp for the slurry (silky finish).2–3 green onions , thinly sliced + sesame seeds — fresh, toasty garnish.
Optional veggies: thin-sliced carrots, steamed broccoli florets, snap peas, or bell peppers. Stir in near the end so they stay vibrant and crisp-tender.
How to Make Slow Cooker Mongolian Beef
Slice the beef: For tenderness, slice against the grain into thin strips. Pat very dry so the cornstarch sticks and the sauce isn’t watery.Dust with cornstarch: Toss beef with 2 Tbsp cornstarch to lightly coat. This is the secret to that velvety, clingy sauce later.Whisk the sauce: In a bowl, combine soy sauce, water/broth, brown sugar, garlic, ginger, vinegar, sesame oil, and red pepper flakes.Load the slow cooker: Add beef and sauce. Stir to coat, then cover.Cook low & slow: Low 6–8 hours or High 3–4 hours, until the beef is tender. (Different slow cookers run hot or cool—peek at the 3-hour mark on High.)Thicken: Stir together 2 Tbsp cornstarch + 2 Tbsp cold water . Pour into the cooker, turn to High , and cook 10–15 minutes until glossy and thick. Sauce thickens more as it cools.Veggies (optional): If adding quick-cook veggies (steamed broccoli, snap peas), stir them in with the slurry so they warm without overcooking.Finish & serve: Top with green onions and sesame seeds. Serve over rice or noodles and enjoy that silky, takeout-style sauce.
Freezer-Meal Prep: Assemble Now, Cook Later
Make it a kit: In a quart bag, whisk all sauce ingredients. In a separate gallon bag, add the cornstarch-dusted beef. Seal both; tuck the small bag into the large one.Label clearly: Write the recipe name, date, “thaw overnight,” and cook time (Low 6–8 hrs / High 3–4 hrs ). Future-you will be grateful.Freeze flat: Freeze up to 3 months. Flat packs thaw faster and stack neatly.Cook day: Thaw in the refrigerator overnight for even, safe cooking. Add contents to the slow cooker and proceed with the steps above.
Food-safety tip: For slow cookers, start with thawed meat so food moves through the “danger zone” quickly. See the USDA’s slow-cooker guidance for details: USDA: Slow cookers & frozen meat .
Storage, Reheating & Make-Ahead Tips
Fridge: Store leftovers airtight for up to 4 days.Freeze: Cool completely and freeze up to 3 months. Thaw overnight in the fridge before reheating.Reheat: Warm gently on the stovetop or in the microwave in short bursts. Add a splash of water or broth to loosen the sauce if needed.
Serving Ideas, Add-Ins & Simple Sides
Base: Jasmine rice, brown rice, cauliflower rice (for low-carb), or lo mein-style noodles.Veggie boost: Stir in steamed broccoli, sautéed bell peppers, or quickly blanched snap peas at the end.Garnish: Green onions, sesame seeds, a drizzle of chili oil for gentle heat.Easy sides: Cucumber salad, roasted green beans, or edamame for quick protein.
FAQ: Slow Cooker Mongolian Beef
Can I make this low carb?
Yes! Swap the brown sugar for a 1:1 zero-calorie sweetener (allulose or a monk-fruit/erythritol blend work well) and thicken with xanthan gum instead of cornstarch (start with 1/4 tsp sprinkled in while stirring; let it sit a few minutes to activate). Serve over cauliflower rice or zucchini noodles.
What cut of beef works best?
Flank steak gives that classic tender-chewy bite and slices beautifully against the grain. Sirloin is great value and turns very tender in the slow cooker. Trim excess fat and slice thin for the best texture.
Can I make it on the stovetop?
Yes. Sear the cornstarch-dusted beef in a large skillet with a little oil until browned (in batches). Whisk the sauce separately, add to the pan, and simmer gently until the beef is tender and the sauce thickens (add a slurry if needed). This version cooks faster and the sauce reduces more quickly.
How do I make it less sweet?
Start with 1/3 cup brown sugar. Add a splash of rice vinegar and an extra tablespoon of soy sauce to balance. You can also stir in a squeeze of lime at the end for a bright finish.
Can I cook slow cooker Mongolian beef from frozen?
No—thaw first. For safety and best texture, thaw kits overnight in the refrigerator before slow cooking (see USDA link above).
Finished Slow Cooker Mongolian Beef
Silky, savory, and perfectly sauced—this is the cozy bowl of food we all crave on a chilly night. If you try it, leave a rating and a comment and tell us what veggies you added or how you served it. Your tweaks help other readers!
More Easy Freezer & Slow Cooker Recipes
1 ½ pounds flank steak sliced across grain into strips ¼ cup cornstarch 2 tablespoons olive oil 1 teaspoon minced ginger 3 cloves garlic minced ⅛ teaspoon crushed red pepper flakes optional ¾ cup low sodium soy sauce ¾ cup water ¾ cup brown sugar ½ cup shredded carrots 3 medium green onions chopped (garnish) Coat flank steak pieces in cornstarch, by either tossing in a bowl or in a bag. If possible, let meat sit after coating in cornstarch for 10-30 minutes.
Heat large skillet to medium-high heat and brown the meat, if desired. Then add the meat to the slow cooker.
Mix together the sauce ingredients - ginger, garlic, soy sauce, water, brown sugar, and carrots. Then pour sauce over meat in the slow cooker.
Cook on high for 2-3 hours or low for 4-5 hours.
Serve over cooked rice or noodles and garnish with green onion, if desired.
Freezer Meal Instructions: Coat flank steak pieces in cornstarch and place in a gallon freezer bag, remove excess air, and seal bag.
Mix sauce ingredients together and place in a quart bag. Keep the two bags together, label, and freeze.
To serve: Thaw in refrigerator overnight. Brown meat in skillet, if desired. Then cook meat and sauce in slow cooker on high for 2-3 hours or low for 4-5 hours.
Calories: 347 kcal | Carbohydrates: 37 g | Protein: 26 g | Fat: 10 g | Sodium: 1142 mg | Fiber: 1 g | Sugar: 28 g
Recipe Adapted From: Once a Month Meals
So glad your family enjoyed it too. Your additions sound great!
For this recipe I combine the ingredients for the sauce and put it in the bag, then add the coated raw steak pieces to the bag as well. Freeze. Then thaw and cook later.
If you use a vacuum seal bags could you keep longer?
Yes, it probably would keep for longer. In my experience, vacuum sealed items do tend to last a little longer in the freezer before freezer burn sets in!
Delicious! Easy to make and freeze.
Thanks for the review, Becca!
My slow cooker digital readout is dying. What is your favorite brand of slow cooker? I saw what America’s Test Kitchen chose but the reviews on Amazon didn’t agree. Now I’m stumped.
Hey Jane, great question! I haven’t used a slow cooker in such a long time, lol. I love using my Instant Pot instead. Sorry I couldn’t be of more help!
The printed recipe and the instructions/quantities in the posted article do not match. if you print this recipe, make sure you go through the entire article and add adjustments to the printed recipe. Apparently the recipe has evolved since the recipe graphic was created.