Preheat oven to 400F. Grease 8 x 8 x 2 inch square baking dish. Brown ground meat and onion.
Stir in taco mix; spoon into baking dish. Beat Bisquick, milk and eggs with whisk or hand beater until almost smooth (about 1 minute). Pour over meat mixture. Bake until knife inserted in center comes out clean (about 25 minutes). Sprinkle with grated cheese; return to oven for a few minutes or until cheese melts. Great with salad and tortilla chips. Serve hot.
Cajun Country -- New Iberia, Louisiana