Like most motherboards these days there are quite a few different ways to overclock your system. The easiest way would be in the TPU section of the Ai Suite III software. Here you change the values for the BCLK Frequency, CPU Ratio, CPU Cache Ratio, CPU Strap as well as all of your voltages.
Moving into the BIOS there is a OC Tuner function that will tune your system. You can set it to tune via BCLK or Ratio.
I selected ratio and the Z87-Expert did its thing and when I booted into Windows it had overclocked the system to 4.3 GHz.
Of course we are going to do our own tweaking in the BIOS to get the best overclock. While I was able to get the system to boot at 4.9 GHz, I had to move things back down to 4.7 GHz at 1.37V on the CPU for a stable system.