Add all of the beans to a colander and drain. Add the corn. Rinse well with cool water. Drain well. Pour into a large bowl.
Finely chop the green onions, using all of white portion and enough tops to measure a little over ½ cup. Add the green onions to the bean mixture.
Pour the olive oil into a 2 cup glass measuring cup. Whisk in in the vinegar, garlic powder, cumin, salt and pepper. Pour over the bean mixture. Stir until well coated. Serve immediately or chill.
Notes
*If you are preparing this recipe as gluten-free, just be sure to use brands of corn and beans that are known to be GF.