I do it until the liquid (when you poke one open) is clear. The whole rely on time and temperature never quite worked for me, poke one and see if it's done!

Also, 45 minutes sounds like a whole chicken, ten-fifteen, yeah ok maybe 20 should do for a breast.

I really want to make some comment here about monster breasts, but 15 to 20 minutes sounds like more than enough, unless they're more than two inches thick.

Lots of ways to do this -

1. When the juices run clear is the classic way. Take out the breasts and poke them with a knife. Watch the liquid that wells up. If it's milky/cloudy, cook the chicken more. If it's clear as water, it's done.

2. About 15 minutes per inch of thickness. So probably about 30 minutes for your breasts.

3. When you start to cook chicken a lot, you can just depress the center part with your finger. It will feel firm with a teeny bit of 'bounce' when done, and wiggly-ish when not yet done.

4. A meat thermometer is a very good friend - even the cheap ones. I tend to use mine only for big roasts and whole birds, but it's handy when you want to be really sure you got it up to temp.

Finally, the food-safety guidelines are a bit needlessly stringent, in my risky opinion. Chicken meat at 170- is overcooked, basically. I seem to remember that outside the US the recommended times are about 5 degrees lower. Since moist chicken is preferable to dry, I don't cook it 'til it's leathery. But you're on your own with that decision - it's certainly a little scary given industrial poultry production, but on the other hand, relatively small risk to a healthy person.

Oh, and finally finally, chicken is dense and holds heat well, which means it continues to cook itself even after you take it out of the oven. So if you're going to have 5 or 10 minutes between pulling it from the oven and dinnertime, pull the chicken out just short of done and let it rest in the pan on the counter. Test it before serving - it'll probably be perfect. If it needs more heat, just pop it back in for a minute, no harm done. But if you cook it all the way and THEN it sits for 10 minutes, you have expensive sawdust.

Uncovered: 20 minutes. Covered: 45 minutes.

It will take 10 minutes just to warm up the Corning dish with the cover.

You could pre-heat the dish though.

Thanks, everyone!

What mischief said makes sense because I always bake them in the Corning dish. They come out very moist (that sounds icky, oh well) and non-sawdust-y.

350 degrees for 20-25 minutes. Uncovered, like mischief said.

A digital kitchen thermometer with the remote probe is $20 soundly invested in Perfect Roasts Forever. Of the several I've tried, the one from Williams Sonoma was the best; it has settings like "chicken" "pork" and "Beef-med" that are correctly calibrated for properly-done food, whereas other brands just list the USDA recommended temps for meats. USDA recommended temperatures are great if you like eating sawdust and leather. But even the plain-jane models are useful, you just subtract 7 - 10 degrees from the suggestions.