Place edamame, corn, onion, garlic, olive oil, salt and pepper into a 13 x 9 pan and stir to combine. Place on middle rack of the oven and roast for 10 to 15 minutes, just until the edamame begins to brown.
Remove from oven and place in refrigerator until completely cool, approximately 30 minutes.
Add tomato, basil and vinegar to mixture and toss to combine. Taste; adjust seasoning as needed. Serve chilled or at room temperature.