Step 1

Preheat the oven to 450 degrees F (230 degrees C).

Step 2

Toss cauliflower, mushrooms, garlic, red onion, red and yellow bell peppers, olive oil, vinegar, salt, and pepper together in a large bowl. Transfer to a 2-quart baking dish.

Step 3

Roast in the preheated oven until cauliflower is fork tender, about 30 minutes. Serve immediately.