This is approximate, and not perfect, but according to Golden Nugget in Vegas, the Big 12 pecking order goes something like this:
1. Texas
2. Oklahoma -0.5 points
3. Oklahoma State -1
4. Kansas State -6
5. TCU -6.5
6. Baylor -9
7. Texas Tech -11
8. West Virginia -12.5
9. Iowa State -16.5
10. Kansas -28
So, in simple terms, Texas, Oklahoma and Oklahoma State are virtually the same team. Texas and Oklahoma are maybe considered slightly better than Oklahoma State. Texas is about 6 points better than K-State; 9 points better than Baylor; 16.5 points better than Iowa State; and 28 points better than Kansas.
You can figure out the difference between each team by doing the math. (i.e., K-State is a half-point better than TCU; 3 points better than Baylor; 5 points better than Texas Tech).