Help roasting a bone in pork loin. 190 degrees F for 3.5-4 hours? 200 degrees F for 2.5 hours? any idea which is correct?

This is the "reverse sear" method, something I've been practicing for several years, for both beef and pork roasts.

You cannot rely on time. Ovens heat differently, some do not maintain the temperature set on the thermostat at the extremes of the appliance's range.

The other major factors include the size of the roast plus the internal temperature at the start, as well as how fast your oven heats up, retains heat when the door is opened, etc.

The only reliable way to do this with little fuss is to use a remote meat thermometer.

Right now, I have a 2.5 lb. beef tri-tip in a 180 deg F oven. It started with an internal temperature of 37 deg. It takes about 10 minutes for my oven to reach 180-200 degrees. I expect it to go about two hours before it reaches the target temperature of 110 degrees where upon I pull it out, tent it for a few minutes, then sear on the grill to reach an internal temp of about 130.

The key is not look at the clock. Look at the internal temperature.

Anyhow, best of luck.

Hi there, it sounds like you are using a "reverse sear" method to cook your pork loin. I ALWAYS use reverse searing for any meat that I want to keep pink in the middle and it hasn't let me down yet! I've done steaks, big thick heritage pork chops, and boneless pork chops. I've never done a loin but I bet it will work great.

The key thing to remember about reverse searing is that the initial low-temp roast step should be done as low as possible, time allowing. There's not a linear relationship between temperature and time, so it's kind of hard to say "if it takes this time at this temperature, it should take that time at x degrees higher." The lower the temperature, the longer it'll take, and the better your results will be, because the loin will cook more evenly. Having said that, it will take longer, so there's a consideration there too. Unfortunately nobody can say exactly how long it'll take at any temperature, so your best bet is to check the meat's temperature starting probably 20 minutes before the recipe suggests it'll take. According to Serious Eats, you want to slow roast the pork till it hits 140°F (60°C), then rest for a bit, then sear. Hope this helps!

That's only a 40%-60% difference in time, but I can't help you, never tried roasting at anything near that low a temperature- seems more typical of the temp. you'd use for pulled pork or something like that. If you give the size of the roast, someone will likely know.