In a pan, put little oil and stir fry onion and bell pepper for 3 mins then add remaining vegies for another 3 mins, drained from oil and set aside.

Same pan with same oil, stir fry meat. When all done, add vegies cook for 5 minutes.

Remaining marinade, add 2 tbsp water and 1/2 tbsp mushroom powder (it's optional) or just add corn flour, then pour to the beef, cook until sauce is thick.. and ready to serve..