Toss 2 cups blueberries in 1 Tbsp. lemon juice, and spread evenly on bottom of a lightly greased 13- x 9-inch baking dish.
Combine oats, next 9 ingredients, and remaining 1 Tbsp. lemon juice in a large bowl, stirring until well blended. Pour oat mixture evenly over blueberries.
Bake, covered, at 350° for 30 minutes; uncover and bake 20 more minutes or until golden brown and set.
Apple-Pecan Baked Oatmeal: Place 1/2 cup chopped pecans in a single layer on a baking sheet. Bake at 350° for 15 minutes or until toasted, stirring once. Omit blueberries and lemon juice. Peel and chop 5 Granny Smith apples. Spread on bottom of a lightly greased 13- x 9-inch baking dish. Sprinkle toasted pecans over apples. Prepare oat mixture as directed, and pour evenly over apples and pecans. Bake as directed.