Chopped up chicken breast and flank steak. Combined with onion, bell peppers and seasoning. How do they cook
I would saute the chicken separately until opaque. I would avoid to combining these ingredients while raw.
"avoid combining" I meant; the reason is the ingredients will cook at different rates. However, if already combined, I think I would just get going and cook it all up together for food safety reasons. Perhaps others will weigh in.
For a novice cook, I recommend cooking the meat separately (as creamtea suggests until opaque), then remove from the pan and set aside.
Cook the other ingredients together to your liking, then add the meat back to the pan, let cook a minute or two longer.
Once you are more experienced, you may be able to cook the meat, then add the veggies before the meat is partially cooked, but it requires some experience since the amount of the vegetables, temperature of your pan, size of the vegetable pieces, and doneness of the meat are all mitigating factors.
Also, you don't want to crowd the pan with too much, otherwise it'll just steam instead of saute (and form that delicious brown crust from the Maillard reaction).
Oops, I intended to say to add the vegetables while the meat is partially cooked so all of it will finish together.
Again, this is something that a more experienced cook will find easy to do.
Anyhow, good luck.
I like to grill the chicken till almost done then finish in the pan with the other ingredients