Can I make the batter for banana bread tonight, but bake it off in the morning? Or will holding it in the fridge like that mess with it?
Definitely do not make the batter in advance. The liquids react immediately with the leavening agents, so you will not get satisfactory results when you try to bake it. Much, much better simply to mix the dry ingredients, leave them on the counter, mix the wet ingredients, refrigerate them, then stir the two together as directed, while your oven is preheating in the morning. ;o)