PREHEAT oven to 425°F. Cut the ends off the Brussels sprouts and cut in half lengthwise. Slice the red onion into ½” wedges. Wipe the mushrooms with a damp cloth and cut in half or quarters (depending on the size). Peel the carrots and cut diagonally into ½” thick slices. Remove the stem end and string from the snap peas
PLACE the prepared vegetables in a large bowl. In a small bowl, whisk together the balsamic vinegar, Dijon mustard, olive oil, garlic powder, thyme, salt, and pepper. Drizzle the dressing over the vegetables and toss until well coated...
SPREAD the vegetables onto one or two baking sheets (be sure not to overcrowd the pan). Bake for 30-35 minutes, until the vegetables are softened and browned. Serve warm.