Step 1

Preheat oven to 450 degrees F.

Step 2

Stir 2 tablespoons oil, 1 tablespoon oregano, half the garlic, 1/4 teaspoon pepper and 1/8 teaspoon salt together in a large bowl. Add Brussels sprouts, gnocchi and onion; toss to coat. Spread on a large rimmed baking sheet.

Step 3

Stir 1 tablespoon oil, the remaining 1 tablespoon oregano, the remaining garlic and the remaining 1/4 teaspoon pepper and 1/8 teaspoon salt in the large bowl. Add chicken and toss to coat. Nestle the chicken into the vegetable mixture. Roast for 10 minutes.

Step 4

Remove from the oven and add the tomatoes; stir to combine. Continue roasting until the Brussels sprouts are tender and the chicken is just cooked through, about 10 minutes more. Stir vinegar and the remaining 1 tablespoon oil into the vegetable mixture.