Heat olive oil in a large Dutch oven or deep skillet over medium heat. Add diced onion and cook for 3-4 minutes until softened and fragrant, stirring occasionally. Then add minced garlic and cook for another minute until the aroma becomes intense and inviting.
Add cubed butternut squash, halved Brussels sprouts, sliced carrots, and diced celery to the pot with the aromatic base. Stir everything together to coat vegetables evenly with the oil and aromatics. This harvest side dish comes together beautifully when all ingredients are distributed consistently throughout the pan.
Pour in the vegetable broth and add the bay leaf, dried thyme, dried sage, salt, and pepper. Stir well and bring the mixture to a gentle simmer. Simmer for 25-30 minutes until the butternut squash is fork-tender and the Brussels sprouts have caramelized slightly at their edges.
Stir in the balsamic vinegar and dried cranberries during the final 3 minutes of cooking. The cranberries will plump up beautifully as they absorb the warm broth. Taste and adjust seasonings if needed—the cozy harvest side recipe should have a perfect balance of savory, sweet, and herbal notes.
Remove the bay leaf before serving. Ladle this warm, heartwarming transition dinner into bowls and drizzle with any remaining broth from the pot. The vegetables should be tender but not mushy, with the cranberries providing bursts of tart sweetness throughout.