Are ounces weight or volume?
 

I'm confused about the quantity listed as oz. Is this weight or volume? For example, an ounce of cheese must be a weight, but an oz of yogurt must be a volume. but sometimes I can't tell! Is there a trick to figuring out which is meant?

A solid food should be weight, but liquids should be volume. Alternatively, you can switch your measurements to Metric, eliminating Imperial confusion.