Combine first 4 ingredients in a large bowl.
Whisk together buttermilk and oil, and stir into baking mix mixture until blended. Stir in chopped bell pepper.
Turn dough out onto a lightly floured surface; knead 1 to 2 minutes. Press dough into an 11- x 7-inch rectangle on a lightly greased baking sheet.
Bake at 400° for 20 to 25 minutes or until golden brown. Allow to cool slightly; invert onto a cutting board, and cut into squares.
