Heat oven to 200 degrees.
Divide popped corn between 2 ungreased 13x9 baking dishes.
Heat brown sugar, margarine, corn syrup and salt until it simmers; stir constantly. Remove from the heat and add baking soda. Pour mixture over the popped corn, stir until coated well. Bake for 1 hour, stirring every 15 minutes.
Note: For a nutty version, decrease the popped corn to 12 cups and add 1-1/2 cups walnuts or pecans, or almonds to each pan.
Submitted by Eric (15) Kentucky