In a bowl or jar, mix together oats, eggnog, yogurt, nutmeg, and salt. Cover and refrigerate for several hours up to overnight. Serve.
You may use regular or Greek yogurt, but if using Greek, it might be necessary to add a bit more eggnog to thin it out. For sweeter overnight oats, you may substitute vanilla yogurt for half of the plain yogurt (I think using all vanilla yogurt and no plain yogurt makes the oats too sweet and overpowers the eggnog flavor, but it's ultimately up to you).
You may add a teaspoon or two of chia seeds or flaxseeds to your oat mixture, if you want to boost the nutrition even more.
You may stir in sliced fruit or berries before refrigerating, or you may top with nuts before serving, if desired.
I prefer using rolled oats, as I think quick oats get too mushy. Steel cut oats are not recommended, as they won't soften adequately.