Remove the husk from the ear of corn and using a sharp knife, remove the kernels from the cob. Place the corn kernels in a small mixing bowl. Add diced red capsicum, zucchini, and thinly sliced onion. Drizzle veggies with 1 tablespoon olive oil and mix until all the veggies are lightly coated with oil. Sprinkle 1/2 teaspoon garlic powder and salt and pepper, to taste, over the veggies and mix well.