In a large nonstick skillet, saute squash and mushrooms in butter until tender. Season with salt and pepper; set aside.
In a bowl, whisk the flour and eggs until smooth. Stir in reserved vegetables and 1/4 cup olives. Coat 12 muffin cups with cooking spray; fill half full with egg mixture. Bake at 450° for 6-8 minutes or until set.
Combine the Parmesan cheese, basil and garlic salt; sprinkle over egg mixture. Combine the onion, tomatoes and remaining olives; spoon over the top. Sprinkle with Monterey Jack cheese. Bake for 5 minutes or until cheese is melted. Serve on English muffins if desired.
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