Melt butter or margarine in a large saucepan. Remove pan from heat; stir in oats, flour, brown sugar, and salt until a dry, crumbly dough forms. Press about 2/3 of the dough into the bottom of 9 inch square pan, making a firm even layer.
Spread cherry pie filling in the crust, and sprinkle with remaining crumb mixture.
Bake for 40 to 45 minutes, until top is lightly browned. Serve warm or at room temperature.