Heat oil in a pan over medium heat.
2. Cook the ham, peppers, and spinach with a pinch of salt and pepper until the spinach has wilted. Transfer to a bowl while you cook the eggs.
3. Stir the 4 eggs with a pinch of salt and pepper, then pour half of the mixture into the pan, swirling it around to make a full circle. Continue on medium heat or flame.
4. Cook for about 15 seconds, then spoon half of the vegetable mixture on one half of the omelet and sprinkle half of the jack and half the cheddar cheese on the other half.
5. Cook until the cheese is half melted, then fold one half of the omelet over the other.
6. Cook for another 15 seconds, then remove and transfer to a plate.
7. Fan out avocado slices on top of the omelets.
8. Enjoy. Serve with salsa if desired.