Bring a large pot of water to a boil. Add the lo mein noodles and cook according to package directions. Drain the noodles and set them aside.
Add the olive oil to a large skillet or wok set over medium heat. Once the oil is hot, add the garlic and white parts of the scallions and cook, stirring, until fragrant, about 2 minutes. Increase the heat to medium-high and add the steak. Cook, stirring, for 1 to 2 minutes.
Add the carrots, broccoli and green parts of the scallions and cook, stirring, until crisp-tender, about 2 minutes.
Add the noodles and prepared sauce and toss to combine. Serve immediately.