How long and at what temp should I oven cook a cut-up whole chicken that was supposed to be cooked at low for 3 hours in a slow cooker?

I prefer to roast chicken at 450. For cut up chicken, it takes about 30 - 45 minutes. Turn after first side gets nice and brown.

Are you wanting to roast or slow cook the chicken? Roasting should be done hot, 450 degrees Fahrenheit is what I like, but that's usually whole and for 45 minutes. I recommend 350 degrees Fahrenheit for 1 hour. Or if you don't want crispy skin, 300 degrees Fahrenheit for 1.5 hours would do it. You could also poach the chicken, that would be the closest texturally to a slow cooker chicken. That can be done in simmering chicken stock for 45 minutes, as a bonus you would get a double stock out of it for risotto or soup. Maybe the best way would be in a metal/ceramic/glass dish, with a cup of water or chicken stock, covered in aluminum foil, at 375 degrees Fahrenheit, for 45 minutes. You won't get crispy skin but it will cook moist chicken.