You should be able to do it in any synth with more than one oscillator. Choose square waves (Quest sounds more like this) or saw waves (Night Flight sounds more like this) and detune them by +/- 5-50 cents (the higher the detune the quicker the 'wobble', experiment to find what you like) each way. Run the result of this through a lowpass filter, you want almost all the higher/harsh frequencies to be removed.
For the quest bass the overall pitch ramps down, so you could put a descending envelope on the pitch control or just use pitch bend in MIDI to get this effect. Then the result will probably need some overdrive or distortion, but nothing too hectic or noticeable. Less is more with this kind of sound, as you're going for a sort of analogue, crispy edge to the low mids and a fatter/louder sub.
Play around with all the settings to get what you like!
