Heat oven to 400°.
Heat margarine in 1-quart shallow round casserole or 8-inch ovenproof skillet in oven until melted.
Place remaining ingredients in blender container in order listed.
Cover and blend on high speed 15 seconds.
Scrape sides; stir to moisten any remaining flour.
Or beat ingredients with hand beater until smooth.
Pour into casserole.
Bake until center is puffed and edge is golden brown, 20 to 25 minutes.
Serve with fresh fruit and sweetened whipped cream or yogurt, if desired.