In a small bowl, whisk together the olive oil, soy sauce, dijon mustard, vinegar, honey, garlic, and 1/4 tsp pepper. Place tenderloin in a reseable plastic bag and pour sauce over top. Place in the refrigerator for at least an hour.
Preheat oven to 400 degrees. Spray a rimmed baking sheet with cooking spray and piece of parchment. Set aside.
Cut off the bottom of the Brussels sprouts and cut them in half. In a bowl, toss them with 2 tbsps olive oil, salt and remaining pepper. Scatter them across your prepared baking sheet leaving room in the center for your tenderloin. Set aside
In a large skillet over medium-high heat, add the remaining tbsp olive oil and heat. Place tenderloin in the pan and cook for about 10 minutes, searing each side using tongs to turn the meat. Transfer meat to prepared sheet pan along with brussels and bake for 25 minutes or until a meat thermometer registers 145. Remove the tenderloin from the sheet pan and place on cutting board to rest for 10-15 minutes. Allow brussels sprouts to roast another 10 minutes, or until crisp on the outside and tender on the inside.
Slice tenderloin and serve along side brussels sprouts.