JJ's restaurant in St. Charles has a pretty decent breakfast offering. Typical diner style breakfast foods and inexpensive, but with a large variety to choose from. Their gravy for biscuits & gravy is very peppery if you like it that way. We have not had a bad meal there. It's a place that the locals gather, we see the same people there all the time.
It is located on Duchesne Dr., just north of West Clay. This is north of I-70, maybe 1/4 mile at the most, and between the Hwy 94 and Zumbehl exits. There is massive construction at 94 & 70, so I would go to the next exit which is Zumbehl, make a right off the ramp and an immediate right onto West Clay which is also the north service road at that point. Go back east on West Clay for maybe 1.5 miles (bad judge of distance!) and Duchesne Drive is at a stoplight just past an apartment complex on the left and there is a used car lot on the NW corner of the intersection. JJ's is right behind the car lot. They serve breakfast until 1:00pm on Sundays, and I think they open at 8.
Might see you there! As this is my first post, I want to state that I am not affiliated with this restaurant in any way, other than a 2x a week customer.
The only other place in St. Chuck that I would recommend is Ginghams, which is on Hwy 94, about 1/4 mile south of I-70. However, the construction in the area would make it very difficult to get to, and since it is next to 3 churchs, Sunday mornings are extremely crowded. It was recently sold, and the quality and service has dropped several notches.
There are not a lot of places that serve breakfast other than fast food and chain buffets in St. Charles. That is one thing that is sorely lacking here - and this area is full of people that love to eat out!
There is a truck stop on the right in Foristell, west of Wentzville, but I have not eaten there so I can't vouch for the food. Other than that, I can't think of anything worth stopping for between St. Charles and Columbia, and there's not much between Columbia and KC either. I second the recommendation of 63 diner in Columbia! Good luck and drive safely!