Cook lo mein noodles according to package directions until tender. Drain and set aside.
Heat oil in a large skillet or wok over medium-high heat.
Stir-fry carrots for 2 minutes until slightly softened.
Add onions and cook for 2 minutes until translucent.
Add broccoli and bell peppers, stir-fry for 3-4 minutes until crisp-tender.
Combine all cooked vegetables and minced garlic in the skillet.
In a small bowl, whisk together vegetable broth, soy sauce, brown sugar, and sesame oil.
Add cooked noodles and sauce to the vegetable mixture.
Toss everything together for 1-2 minutes until heated through and well combined.
Serve immediately while hot.