Judy I used some heart smart round steak that was on special in Woolies this week.
It was pretty tender. But any stir fry type beef would work, or chicken.
LOL I have a couple of asian grocers at the local shops so should have been more adventurous, but the kids all absolutely love capsicum so I thought it was a safe start.
Though you could use any kind of stir fry type veg. But do think the capsicum, carrot, celery combination they chose worked really well.