Yes. As a former bakery owner, I would make my muffin batter the night before and bake them in the morning. Keep this in mind for the holidays - think fresh-baked muffins on Thanksgiving or Christmas Morning. But without making a huge mess in your kitchen the second you get up. Resting the batter for several hours or even overnight gives the starches in the flour more time to absorb the moisture from the liquid ingredients used in the batter.