1. Preheat oven to 375°.
2. Heat a large skillet over medium-high heat. Add oil to pan; swirl to coat. Add onion; cook 2 minutes. Add squash and pepper; sauté 10 to 12 minutes or until squash is golden brown. Remove from heat.
3. Combine cream cheese and milk in a large bowl, stirring with a whisk until smooth. Add eggs, stirring with a whisk. Stir in squash mixture, cheese, and half the crushed crackers. Spoon squash mixture into a 2-quart casserole dish coated with cooking spray.
4. Top with remaining crushed crackers. Bake at 375° for 30 minutes.