Gather all your ingredients. Thinly slice the beef sirloin against the grain into bite-sized pieces. Wash and chop the vegetables: slice the bell pepper, cut the broccoli into florets, and julienne the carrots. Mince the garlic and ginger, and set aside.
In a small bowl, whisk together the soy sauce, cornstarch, and water until smooth. This will be your stir fry sauce, giving the dish that perfect glossy finish.
Place your wok or skillet over medium-high heat and add the vegetable oil. Allow it to heat up until it shimmers, ensuring a nice sear on the beef.
Add the sliced beef to the hot wok in a single layer. Let it sear for about 2-3 minutes without stirring, allowing it to brown. Once browned, stir it for another minute until fully cooked. Remove the beef from the wok and set aside.
In the same wok, add a touch more oil if needed, then toss in the minced garlic and ginger. Sauté for about 30 seconds until fragrant. Next, add the bell pepper, broccoli, snap peas, and carrots. Stir fry for about 3-5 minutes until the vegetables are tender-crisp.
Return the cooked beef to the wok with the vegetables. Pour in the prepared stir fry sauce, tossing everything together to coat. Cook for an additional 2-3 minutes, allowing the sauce to thicken and cling to the beef and veggies.
Once everything is well combined and heated through, serve your Beef and Vegetable Stir Fry over cooked rice or noodles. Enjoy the vibrant colors and delicious flavors that come together in every bite!