Is it normal for my dog's pooping time to vary greatly after meals?

Hi and thanks for using Petco Pet Education Center, formerly Petcoach! This sounds very normal and typical. Just like with any biological system that is so complex, elimination habits are going to be variable depending on many factors such as composition of the food ingested, digestion, absorption of nutrients, and the transit time of the material in the intestines. As long as everything else is normal, it's completely within normal limits for times of elimination to vary. Just think about yourself and your patterns and understand that with very complex physiological systems, variability will always be present and probably normal. I hope this helps rest your mind about Soska.