In a small bowl, whisk oil, lime juice, chili powder, cumin, salt, and pepper until combined. Set aside.
In a large mixing bowl, combine corn, beans, tomatoes, bell pepper, and onion in a medium bowl.
Pour the dressing over the salad and toss to combine. Generously season with salt & pepper. Chill for at least 1 hour.
Top with feta and additional cilantro if desired.
