I can't find the posting and I don't remember where it was but there was somebody who said he/she liked spinach and that he/she gives it to his/her birds. Spinach is very good for people but not good at all for birds because of the high iron content.
When you are trying to decide whether some type of raw or frozen produce is good for everyday, sometimes or never, you need to take into consideration three things:
1. Just because it's good for people, it's not necessarily good for birds
2. Just because something is not toxic, it's not necessarily good when fed often
3. Just because the bird likes it, it doesn't mean it's good for it
Always look at the nutritional values of the item and for these things in particular:
- low protein
- low fat
- high fiber
- high moisture
- extra low iron
- low oxalates
If you keep within these parameters and offer a varied diet [making sure the bird gets different 'colors' every day], you'll do just fine.