Hide the Veggies Please! Summer Squash and Zucchini Corn Casserole

1 tablespoon vegetable oil

2 cups chopped yellow summer squash

1 ½ cups shredded zucchini

¼ cup chopped red onion

1 tablespoon garlic powder

⅛ teaspoon ground black pepper, or to taste

¼ cup grated Parmesan cheese

½ cup light margarine

1 (8 ounce) package cream cheese, softened

1 (14.5 ounce) can whole kernel corn, drained

2 (14.5 ounce) cans cream-style corn, divided

2 (8.5 ounce) packages dry corn muffin mix

2 eggs

1 tablespoon white sugar

Preheat oven to 375 degrees F (190 degrees C). Grease a 9x13-inch baking dish.

Heat vegetable oil in a large saucepan over medium-high heat. Cook and stir yellow summer squash, zucchini, and red onion in hot oil until softened, about 10 minutes; season with garlic powder and black pepper. Stir Parmesan cheese into the squash mixture. Turn off the heat and add margarine and cream cheese, breaking them into smaller pieces as you stir them into the squash mixture; remove the saucepan from heat. Stir kernel corn and 1 can cream-style corn through the squash mixture.

Stir remaining can of cream-style corn, dry corn muffin mix, eggs, and sugar in a large bowl until thoroughly mixed. Add the cooled squash mixture, 1 to 2 cups at a time, until completely integrated; pour into prepared baking dish.

Bake in preheated oven until browned and bubbling on the edges and firm on top, 30 to 50 minutes. Allow to cool at least 5 minutes before serving.