1Heat oven to 350° F. Spray 13x9 inch pan with cooking spray. In large bowl, stir Bisquick mix, mustard, milk and egg until mixed. Pour and spread into pan.
2Bake 15 to 17 minutes or until toothpick inserted in center comes out clean. (Top will not brown.) Remove from oven.
3Meanwhile, in 10-inch skillet, heat oil over medium heat. Cook bell pepper and onion 3 to 4 minutes, stirring occasionally, until crisp-tender. Stir in barbecue sauce and beef. Cook until hot. Spread over baked bread base. Top with cheese and pickle slices.
4Bake 5 to 6 minutes or until cheese is melted. Cut into squares.