Preheat oven to 350 degrees.
Heat olive oil in a skillet until fragrant. Add zucchini and onion and heat, stirring occasionally, for about 8 minutes or until softened.
Meanwhile, in a medium bowl, whisk together eggs, milk, rosemary, oregano, garlic salt, and pepper.
Lightly spray a casserole dish with cooking spray. Add zucchini, onion, and cherry tomatoes. Top with half of shredded gouda.
Evenly pour egg mixture over vegetables. Sprinkle remaining gouda over the top.
Bake for 30 minutes or until the center is set. If desired, broil for 2 - 3 minutes to brown the top.
Enjoy!