There are many ways to cook a deer tenderloin but I like to cook mine in the oven so that it doesn’t dry out. I marinate mine in whatever I feel like at the time and then I wrap the loin tightly in tin foil. Put into a 350 degree oven and check it after 45 minutes. Stick a thermometer into the thickest part and when the thermometer reads 155 degrees, pull it out. Seal the loin back up and allow to sit on top of the stove for 20 minutes. It will continue to cook and will reach 160-165 degrees.