Yep.  You have secondary taps for 4, 8, and 16 ohms.  It's just a matter of wiring up 4-ohm tap.  You can swap it out with another tap on the current impedance selector or get a rotary switch and have all three options.

As for the cabinet you are using, keep in mind that modern bass amps are typically full range amps using flat response speakers, the same as PA's and keyboard amps.  Guitar amps and speakers, in turn are tuned to enhance the limited, midrange-based, tonal range of the electric guitar.  So, using a guitar amp with a modern bass cab may sound really flat and lifeless.  But it certainly does no harm to try.

If it's an older bass amp cab, so '70's or earlier, you should be fine, they usually use guitar loudspeakers, depending on the manufacturer.