From three quasar samples with a total of 1038 objects in the redshift range 1.0 to 2.2 we measure the variance sigma squared of counts in cells of volume Vu. By a maximum-likelihood analysis applied separately on these samples we obtain estimates of sigma squared (l), with l identically equal to Vu1/3. The analysis from a single catalog for l = 40/h Mpc and from a suitable average over the three catalogs for l = 60, 80, and 100/h Mpc, gives sigma squared (l) = 0.46 + or - 0.27, 0.18 + 0.14 or - 0.15, 0.05 + 0.14 or - 0.05, and 0.12 + 0.13 or - 0.12, respectively, where the 70% confidence ranges account for both sampling errors and statistical fluctuations in the counts. This allows a comparison of Quasar (QSO) clustering on large scales with analogous data recently obtained both for optical and Infrared Astronomy Satellite (IRAS) galaxies: QSOs seem to be more clustered than these galaxies by a biasing factor bQSO/bgal approximately 1.4 to 2.3.