In the morning: Cook blueberry compote. Finish oatmeal.
1. Combine blueberries, sugar, rind, juice, and 1/4 teaspoon cinnamon in a medium bowl; toss to coat. Refrigerate.
2. Bring 4 cups water to a boil in a medium saucepan. Stir in remaining 1/4 teaspoon cinnamon, oats, and salt; cook 1 minute. Remove oat mixture from heat, cover, and refrigerate in pan overnight.
3. Bring blueberry mixture to a boil in a small saucepan over high heat. Cook 6 minutes or until slightly thickened, stirring frequently. Bring oat mixture to a boil over medium-high heat; cook 5 minutes or until thoroughly heated, stirring frequently. Add butter to oat mixture. Spoon 3/4 cup oatmeal into each of 4 bowls; top each serving with 1/4 cup blueberry compote.