Preheat oven to 375 degrees. Get ready to bake crust to room temperature, about 20 minutes out of the refrigerator. Put pie crust into a pie pan and set aside.
Add squash, zucchini, tomatoes, onion and ham in a skillet and saute in a tablespoon of olive oil. Cook until tender. In a small bowl, whisk together milk, cheese, cornstarch, salt and pepper. Pour into pie crust. I like to sprinkle about a cup shredded cheese on top.
Bake at 375 for 25-30 minutes until golden brown on top. Let cool for 10 minutes before serving.