Lay pork tenderloins out on a rimmed baking sheet.
Mix olive oil, salt, pepper, and rosemary together in a small bowl.
Rub each tenderloin with rosemary mixture, covering each tenderloin completely. Using your hands for this step is most efficient and effective.
Place in oven and roast for 15 minutes.
Cook the tenderloins for 20-30 minutes*, turning once after the first 12 minutes.
Remove from oven when the internal temperature of the thickest part of the tenderloin reaches 145°.
Once out of the oven, tent tenderloins with foil for about 5 minutes before slicing.
Use a sharp knife to slice the pork into ½ inch pieces and serve.
Notes
Use an instant read digital meat thermometer to measure the internal temperature of the tenderloin. This is to prevent overcooking the pork.*Cooking time will vary depending on the size of each tenderloin. Remove from oven when the thickest part of the tenderloin reaches 145 degrees.A smaller tenderloin (about 13 ounces) will likely be finished cooking in about 20 minutes.If you use a cut of pork that is thicker than one pound (like pork loin), cooking time will increase. In this case, continue to turn every 10-15 minutes while roasting, until an internal temperature of 145 degrees is reached.