Heat 1 teaspoon olive oil in a large sauté pan over medium-high heat. When hot, add the onion, peppers and garlic. Cook, stirring occasionally, for 5 to 6 minutes, until the vegetables are wilted and slightly browned. This can be done up to 3-4 days in advance. Store in the refrigerator until ready to prep the casserole.
Preheat the oven to 350°F.
In a large bowl, stir together the precooked onion and bell pepper mixture, corn, kale, chicken, mayo, salt and pepper until combined.
Transfer the chicken mixture to a 3-quart (9X13) rectangular casserole dish, then top with the cheddar cheese and bacon.
Bake for 30 minutes, until the cheese is browned and bubbling.
Meanwhile, slice the green onion and set aside.
After removing the casserole from the oven, let it cool slightly, then garnish with green onions and serve!