To prepare relish, brush oil over corn and bell pepper. Place corn and bell pepper on grill rack coated with cooking spray; grill 20 minutes or until lightly browned, turning every 5 minutes. Place bell pepper in a zip-top plastic bag; seal. Let stand 10 minutes. Remove pepper from bag; peel and chop. Place pepper in a large bowl.
Cut kernels from ears of corn to measure 2 1/2 cups; add to bell pepper. Stir in onion and next 4 ingredients (through 1/4 teaspoon salt).
To prepare steak, combine 1/2 teaspoon salt, onion powder, and next 7 ingredients (through black pepper); rub salt mixture evenly over steaks. Place steaks on a grill rack coated with cooking spray; grill 5 minutes on each side or to desired degree of doneness. Serve with relish.