Heat oven to 425°F. Toss the Brussels sprouts with 1 tbsp olive oil, 1/4 tsp salt and the pepper on a large rimmed sheet pan; arrange cut-side down. Roast 12 minutes.
Meanwhile, whisk the honey, balsamic vinegar, remaining 1 tbsp olive oil, garlic, thyme and remaining 1/2 tsp salt in a small bowl.
Pat the pork tenderloin dry and brush it all over with half the glaze. Pull the pan from the oven, push the sprouts to the edges, and set the pork in the center with the pear quarters nestled around it.
Roast 18 to 22 minutes, until the pork reaches 145°F in the thickest part and the pears and sprouts are tender and caramelized.
Brush the pork with the remaining glaze, tent loosely with foil and rest 5 minutes. Slice into 1/2-inch medallions and spoon the pan juices over the pears and sprouts before serving.