Alot of the units get pretty heavy pressure by 2nd and 3rd season they have been hunted pretty hard. Having gone through several season including BP and Archery, they usually are in the nastiest steepest stuff they can find OR on private or hard to get to areas. Keep in mind that last year only 23% of the tags were filled if you looked at all seasons and methods. Granted this counted archery which is lower than rifle, but dont consider of cow tag as a gimmie.

Also keep in mind that you cannt buy an OTC Cow tag, would have to be a leftover tag. Check the website to see whats available still for those units.
http://wildlife.state.co.us/LeftoverLicense.htm