Heat the olive oil in a large skillet over medium-high heat.
Add the thinly sliced beef in batches, browning it on both sides for 1-2 minutes per side. You don’t need to cook the beef all the way through; just give it a nice sear for extra flavor.
Once browned, transfer the beef to the slow cooker.
2. Prepare the Sauce:
In a medium bowl, whisk together the soy sauce, oyster sauce, beef broth, brown sugar, cornstarch, sesame oil, garlic, ginger, rice vinegar, black pepper, and crushed red pepper flakes.
Pour the sauce mixture over the beef in the slow cooker, and give it a good stir to coat the beef evenly.
3. Slow Cook:
Cover the slow cooker and cook on low for 4-6 hours or high for 2-3 hours, until the beef is tender and the sauce has thickened.
4. Add the Broccoli:
About 30 minutes before serving, add the broccoli florets to the slow cooker and stir them into the sauce. If you’re using fresh broccoli, be sure to cook it just enough to remain crisp-tender. If you’re using frozen broccoli, add it a bit earlier so it cooks through.
5. Serve:
Once the beef is tender and the broccoli is cooked, serve the Slow Cooker Broccoli Beef over steamed rice (white, brown, or jasmine rice works great).
Optionally, garnish with a sprinkle of sesame seeds or chopped green onions for added texture and flavor.
