HEAT oven to 350°F.
MIX cracker crumbs and margarine; press onto bottom of 13x9-inch pan sprayed with cooking spray. Bake 8 to 10 min. or until golden brown. Cool 5 min.
SPRINKLE 1 cup mozzarella over crust; top with peppers and remaining mozzarella.
WHISK eggs, milk, mustard and parsley until blended; pour over ingredients in pan. Sprinkle with Pecorino Romano.
BAKE 30 to 35 min. or until center is set. Cool 10 min. before cutting into bars. Serve warm.