Preheat oven to 425 degrees F. Place bell peppers in a large 9x13 baking dish, drizzle with 2 tablespoon olive oil and toss with a spoon to coat evenly.
Then sprinkle with salt and pepper, toss again and flatten into a single layer as much as possible. Bake for 25-30 minutes or until peppers are soft when pierced with a knife and have some blistered spots. They will collapse after.
Remove from the oven, drizzle with 1 tablespoon of oil and 2 tablespoon balsamic vinegar, add garlic, and toss to coat.
Transfer to a serving platter along with juices and sprinkle with fresh basil and more finishing salt, if you wish.
Serve as a side dish, as an appetizer with bread and cheese or on top of crostini with whipped ricotta.
Notes
To store leftovers: You can keep leftovers in an airtight container in the refrigerator for 4-5 days. Eat cold or you can reheat them in the microwave for a quick side.
Can I freeze mini bell peppers? I would not recommend to do so because their texture will change significantly.