Cook the noodles according to package directions in a large pot of boiling water. Drain and set aside.
Heat 1 tablespoon of the oil in a large skillet over medium-high heat. Add the sliced beef and cook for 2 to 3 minutes until browned but not fully cooked through. Remove the beef to a plate.
Add the remaining tablespoon of oil to the skillet. Stir in the mixed vegetables, garlic, and ginger. Cook for 4 to 5 minutes until the vegetables are crisp-tender.
Return the beef to the skillet. Pour in the teriyaki sauce and stir everything together. Cook for 1 to 2 minutes until the beef is cooked through and coated.
Add the drained noodles to the skillet and toss to combine. Remove from heat.
Sprinkle with sliced green onions and sesame seeds before serving.