Nebraska's schedule against OK & TX is the same as most of the north teams - every year they play one of the two. ISU and KU are the two exceptions that play both traditional power schools on a two year on followed by a two year off cycle. The difference is that when KU plays them, it's one at home and one on the road. ISU's schedule is either both at home or both on the road.
And, I believe it's usually in consecutive weeks. A quick look at the schedule shows that since 2002, only 2003 and 2006 were not consecutive--'03 went OU, @ TTU, UT; '06 went @ UT, UNI, Nebby, @OU. 2010, 2011, 2014, and 2015 (as far as our known conference schedule goes out), all feature back-to-back weeks against UT and OU. Not going to take the time now to see if other schools have this...but it makes for a rough stretch.