This work studied the effect of composition of powders and water content on mixture quality (MQ) of three binary powder mixtures with good (salt/paprika or salt/sugar) or poor mixing (salt/oregano) behaviour. The mixing behaviour was assessed using coefficient of variation. Results showed that mixture composition did not influence the MQ of sugar/salt and paprika/salt within 20-80% salt content range but it did influence the MQ of oregano/salt with a progressive dis-improvement in MQ with higher oregano content and also for low concentrations of 1% salt. Water content did have an effect on mixing behaviour. When paprika with high water activity (a_w) was mixed with salt, the time required to reach good MQ was longer because of the increased cohesiveness and when oregano with high a_w was mixed with salt it displayed improved MQ because salt particles were able to stick onto the larger oregano particles and reduced segregation.