1) Whisk ingredients together in a small bowl and refrigerate for at least 30 minutes.

2) Heat oil in a large frying pan over medium heat.

3) Add beef and saut for 3-4 minutes just to brown it on all sides.

4) Remove from pan and set aside.

5) Add vegetables and saut for 5 minutes more, until beginning to soften.Stir in teriyaki sauce and allow mixture to come to a simmer.

6) Add beef and any drippings that have accumulated on the plate. Cook for 5 minutes, stirring occasionally.In a small bowl, combine cornstarch with 2 tsp cold water to dissolve. Stir into the pan of beef and vegetables. Allow the mixture to simmer and thicken for 2 minutes. Toss to evenly coat vegetables and beef in teriyaki sauce.

7) Serve.