Combine 2⅓ cups oats, 2 cups milk, 1 cup yogurt, 2½ tablespoons maple syrup, 1 tablespoon poppy seeds, 2 teaspoons vanilla, 2 teaspoons lemon zest, 1 teaspoon lemon juice and ¼ teaspoon salt in a medium bowl; stir well.
Cover and refrigerate until slightly thickened, about 30 minutes.
Divide the oat mixture among 4 (8-ounce) jars (about 1 cup each).
Cover and refrigerate the jars for at least 8 hours.
Garnish with additional lemon zest before serving, if desired.
