Putting scope probes directly onto the crystal leads will probably load the crystal enough to stop the oscillator,and the waveforms at the crystal are not nice square waves but very distorted sawtooth types.Especially with a 30 Mhz bandwidth scope.Its probably better to add some code to drive an output pin from the internal timer/counter which will give the clock divided by some set amount,the standard 8051 increments the counter every 12 clock cycles.