This easy Beef and Onions stir fry is packed with flavour! Made with simple pantry ingredients, you’ll have dinner ready in a jiffy. This beef onion stir fry is perfect as a quick weeknight dinner or as a meal prep.
In a large bowl, combine the sliced beef, cornstarch, oyster sauce, and salt. Let the beef marinate for at least 30 minutes.
In a measuring cup, mix together the soy sauce, ketchup, Worcestershire sauce, oyster sauce, and mirin with 3 tbsp of water. Set aside.
Once the beef is ready, heat the oil up in a large skillet on medium-high and add the beef in a single layer. Sear for 2 to 3 minutes per side, depending on the thickness of your slices. Do this in two batches if needed. Set aside when done.
In the same pan, add the rest of the olive oil and the chopped onions. Let it cook untouched for 2 to 3, like the beef, so it can get a bit of a sear on it as well before sautéing until softened.
Add the beef back to the pan.
Add in the prepared sauce and let it cook for 2 to 3 minutes. It should bubble. Toss to coat everything evenly in the sauce.
Top with garnish if desired. I used green onions and sesame seeds.