Pubs in St. Charles, MO
The Pine Room has plate lunches and great hamburgers, also great fried chicken. The Corner Bar(home of cocked hat bowling) has good burgers. When I first read your post I thought you were looking for English or Irish Pub food. A lot of people like Tubby's Pub 'n Grub at the Plaza Lanes but I haven't been there in ages.
On my list to try because they have home made pie is O'Fallon Bowl Restaurant and Lounge.