Spray the inside of the slow cooker with non-stick cooking spray.
In a large mixing bowl, combine eggs, milk, salt, pepper, and garlic powder; beat well until completely mixed together.
Add broccoli, sliced peppers, mushrooms, onions and garlic to the slow cooker; stir in the egg mixture.
Cover and cook on HIGH for 2 - 2½ hours (cooking times will vary with each slow cooker). Start checking omelet at 1 hour 30 minutes. Omelette is done when eggs are set.
If desired, sprinkle with cheese and cover; let stand 2 to 3 minutes or until cheese is melted. Turn off the slow cooker.
Cut the omelette into 12 wedges and transfer to a serving plate.
If using, garnish with chopped tomatoes, salsa, and parsley. Enjoy!
Recipe by Tone and Tighten at https://tone-and-tighten.com/slow-cooker-vegetable-omelet.html