Preheat oven to 450°.
Remove stems from caps; finely chop mushroom stems to measure 1/2 cup. Set mushroom caps aside.
Heat a large nonstick skillet coated with cooking spray over medium-high heat. Add chopped mushroom stems and garlic; sauté 3 minutes, stirring often. Add wine; cook 2 minutes or until liquid evaporates. Remove from heat; cool 3 minutes. Add cheeses, onions, and peppers; stir until smooth. Spread cheese mixture evenly into mushroom caps.
Combine egg substitute and flour in a small bowl; stir well with a whisk. Place breadcrumbs in a shallow dish. Working with one mushroom cap at a time, dip, cheese side up, into egg mixture; dredge in breadcrumbs, coating only the mushroom cap. Place mushroom cap, cheese side up, on a baking sheet coated with cooking spray. Repeat procedure with remaining mushroom caps, egg mixture, and breadcrumbs. Lightly coat stuffed mushrooms with cooking spray. Bake at 450° for 25 minutes or until tender and lightly browned.