Preheat your oven to 350°F (175°C). Grease a 2-quart baking dish with cooking spray or butter.

In a large skillet over medium heat, add olive oil. Once hot, add the chopped onion and sauté for about 3 minutes until translucent.

Add the sliced yellow squash and zucchini to the skillet. Season with salt, pepper, and garlic powder. Cook for about 5-7 minutes until the vegetables are tender. Remove from heat and let cool slightly.

In a large bowl, combine the beaten eggs, milk, and half of the shredded cheddar cheese. Mix well.

Stir in the sautéed vegetables and crushed crackers into the egg mixture until fully combined.

Pour the mixture into the prepared baking dish. Top with the remaining cheddar cheese.

Bake in the preheated oven for 25-30 minutes, or until the top is golden and bubbly.

Remove from the oven and let cool for 5 minutes before serving. Garnish with fresh parsley if desired.