Preheat the oven to 350 degrees F. Butter a 9-by-13-inch rectangular pan. Mix together the butter, flour, oats, brown sugar, baking powder and salt. Press half the oat mixture into the prepared pan. Spread with the strawberry jam. Sprinkle the other half of the oat mixture over the top and pat lightly. Bake until light brown, 30 to 40 minutes. Let cool completely, and then cut into squares.