Same. I am consistently getting 80-100% of required meals cooked in time for "eat" schedules. This is despite more than adequate cookers, fridges, and cooks. In fact, the cooks are often idle in the hour leading up to the "eat" time, during which they should be making more meals. Usually then about 30-45 minutes prior to the end of the eat schedule, the cooks start to make the remaining required meals, though they frequently aren't ready in time to be delivered to the canteens (right next door) with sufficient time for the hungry prisoners to eat before meal time is up. I didn't have this issue when my most recent prison was smaller and when everyone was just getting medium/medium meals. With a larger prison and my min sec prisoners getting high quantity / medium variety meals, this is more of a problem. However, the bugs prior to The Rock 1.04 prevented me from growing my prison, so I'm not sure if it's the larger size/meal changes or the 1.04 patch that created the problem. I'm playing no mods, only DLC is cleared for transfer.
One other possible observation. It seems like when the cooks produce a lot of food waste (drop ingredients on the floor), they tend to be more likely to come up short of the required meals. If there isn't as much food waste, there seems to be a better chance the proper number of meals are will be ready. So, I wonder if the game counts the total number of food items grabbed (from the boxes on the fridges) rather than the total number of food items that actually make it into the pots/pans and contribute to meals when decided how much food to cook. Thus, when there's food waste, the total number of meals ends up short because not all the ingredients that were grabbed ended up being cooked.