Heat a wok or large skillet on high heat and add the oil. Toss the marinated beef and garlic into the pan. Cook for about 1 minute, continually moving the beef so it browns on all sides. Once the beef is seared, add the broccoli and cook for an additional minute. Stir in the sauce and keep it all moving. Don't be afraid to scrape any bits off the bottom of the pan before they start to burn. Once the sauce has turned into a nice thick glaze, about 1 minute, serve immediately.