Heat the oven to 375°F. Lightly oil a small baking dish with some of the olive oil.
Warm the remaining olive oil in a skillet over medium heat. Add the chopped Brussels sprouts and onion. Cook for 4 to 5 minutes, stirring often, until softened. Set aside to cool slightly.
In a large bowl, combine the ground turkey, cooked Brussels sprouts and onion, dried cranberries, breadcrumbs, egg, Dijon mustard, thyme, salt, and black pepper. Mix gently until everything is evenly combined.
Transfer the mixture to the prepared baking dish. Shape it into a compact loaf, then bake until the center reaches 165°F, about 45 to 55 minutes.
Let the meatloaf rest for 5 to 10 minutes before slicing. This helps the slices hold together.