Brush the ears of corn with butter, and season with chili powder and salt. Place the corn directly onto the grill. Turn the corn occasionally while grilling, cooking until tender and slightly charred on all sides. Cool to the touch, then cut the kernels off the cob to be used in the salad. Discard the cob.
In a bowl, combine the grilled and fully cooled corn kernels with the diced onion, roasted red bell pepper, cucumber, black eyed peas and capers. Sprinkle with lemon juice, season with salt and pepper. Serve chilled.