Hey y’all! If you’re searching for a mouthwatering weeknight dinner that’s rich, tender, and absolutely bursting with sweet and savory flavors, this Slow Cooker Mongolian Beef is just what you need. It’s a set-it-and-forget-it recipe that transforms flank steak into buttery soft slices coated in a sticky, garlicky sauce—all from your trusty slow cooker. Whether you’re making this for a family dinner, potluck, or meal prep, you can count on happy faces and empty plates. Let’s get cooking!

Why You’ll Love This Slow Cooker Mongolian Beef

Perfectly tender beef every time, thanks to gentle slow cooking.
Just 15 minutes of prep—let the slow cooker do the hard work!

Packed with bold, restaurant-style flavors you crave at home.
Great for meal prep and freezer-friendly for busy weeks.
Versatile—serve over rice, noodles, or steamed veggies.

Ingredients for Slow Cooker Mongolian Beef

2 pounds flank steak, thinly sliced against the grain
1/2 cup low-sodium soy sauce
1/2 cup dark brown sugar, packed
1/3 cup hoisin sauce
1/4 cup water
2 tablespoons cornstarch
1 tablespoon sesame oil
3 cloves garlic, minced
1 thumb-sized piece of ginger, peeled and grated (about 1 tablespoon)
1/2 teaspoon crushed red pepper flakes (optional, for heat)
4 green onions, cut into 1-inch pieces (plus extra for garnish)
2 tablespoons toasted sesame seeds (for garnish)

How to Make Slow Cooker Mongolian Beef

Step 1: Prepare the Beef

Trim any excess fat from the flank steak and slice into thin strips, cutting against the grain for the most tender bite. For extra ease, partially freeze the beef for about 20 minutes before slicing.

Step 2: Make the Sauce

In a mixing bowl, whisk together soy sauce, brown sugar, hoisin sauce, water, sesame oil, garlic, ginger, and red pepper flakes.

Step 3: Combine and Start the Slow Cooker

Add sliced beef to the slow cooker. Pour the sauce over the beef and toss gently to coat. Cook on LOW for 4–5 hours or HIGH for 2–2.5 hours, until beef is melt-in-your-mouth tender.

Step 4: Thicken the Sauce

About 30 minutes before serving, whisk cornstarch with 2 tablespoons cold water. Stir into the slow cooker and add the green onions. Let cook until sauce thickens.

Step 5: Serve and Garnish

Give the Mongolian beef a good stir, then serve hot over steamed rice or noodles. Garnish with toasted sesame seeds and extra green onions for crunch and color.

Prep Time: 15 minutes
Cook Time: 4–5 hours (LOW) or 2–2.5 hours (HIGH)
Total Time: 4.5–5.25 hours

Notes for Perfect Slow Cooker Mongolian Beef

For information on proper slicing, check out this handy guide on slicing flank steak.
If your sauce is too thin, you can add a bit more cornstarch (mixed with water) and cook lid-off for the last 15 minutes.

Want to lower sodium? Swap in coconut aminos and use reduced-sodium soy sauce—see more on soy sauce nutrition here.

Variations of Slow Cooker Mongolian Beef

Gluten-Free Mongolian Beef: Use gluten-free tamari instead of soy sauce and gluten-free hoisin.
Veggie Mongolian Beef: Add bell peppers, snap peas, or broccoli in the last hour for extra texture and color.

Spicy Mongolian Beef: Stir in a tablespoon of sriracha or more red pepper flakes for an extra kick.

Equipment Needed for Slow Cooker Mongolian Beef

4-6 quart slow cooker
Sharp knife
Cutting board
Mixing bowls
Measuring cups and spoons
Whisk

How to Store Slow Cooker Mongolian Beef

Let leftovers cool, then transfer to an airtight container. Store in the refrigerator for up to 4 days. For longer storage, freeze in freezer-safe containers for up to 2 months. Thaw overnight in the fridge and reheat gently on the stove or in a microwave, adding a splash of water if needed to loosen the sauce.

Serving Suggestions for Slow Cooker Mongolian Beef

Serve over fluffy steamed Jasmine or basmati rice.
Try with noodles (like lo mein or udon) for an extra-hearty meal.

Pair with crisp Asian slaw, steamed broccoli, or sautéed bok choy.
For a complete takeout-style vibe, enjoy with homemade egg rolls or dumplings.

Pro Tips for the Best Slow Cooker Mongolian Beef

Slice beef thinly and against the grain—a must for fork-tender texture (learn why here).

Don’t skip thickening the sauce with cornstarch; it brings that iconic glossy finish.
Add green onions late so they stay bright and fresh, not mushy.