In a large baking dish, toss grape tomatoes, potatoes, bell peppers, and red onion with one tablespoon olive oil and chopped garlic.
Mix well until incorporated and salt and pepper to taste.
Place the sausage links on top of the vegetables. Place sprigs of thyme throughout the dish. Cover with foil and bake for 90 minutes.
Remove tinfoil from baking dish, mix vegetables around, and bake for an additional 30 minutes until sausage is golden brown. (*You may need to turn the sausage to prevent from burning). Serve immediately.