First things first, temperature is your best friend. Forget timers for a second—though we’ll use them. For an 8-pound bone-in turkey breast, you’re looking at roughly 2 hours and 45 minutes to 3 hours and 15 minutes in a 325°F oven.
But don’t just set a timer and walk away. That’s how you end up with dry, sad turkey. Your only real job is to make sure the internal temperature hits 165°F in the thickest part of the meat. A meat thermometer is the hero of this story, not the oven.
If you bought a boneless breast (about 4-5 pounds), cook time drops to roughly 1 hour and 45 minutes to 2 hours. But since you said 8 pounds, I’m betting it’s bone-in. More flavor, more drama. Love it.