A method of improving the stability and broadening the range of pH stability of an aqueous solution of from about 0.001% to 5% by weight of a water soluble organosilane containing hydrolyzable groups such as methyltrimethoxysilane, 3-(trimethoxysilyl)propyldimethyloctadecyl ammonium chloride and 3-(trimethoxysilyl)propylmethyldi(decyl) ammonium chloride by the use of 0.05% to 10% by weight of a water soluble organic quaternary ammonium compound having at least one nitrogen-bonded hydrocarbon group of at least 8 carbon atoms and being free of silicon atoms, such as benzalkonium chloride, along with from about 0.5% to 30% by weight of at least one surfactant selected from the group consisting of nonionic, amphoteric sarcosine anionic, and cationic surfactants other than the water soluble quaternary ammonium compounds. The pH of the solution can be adjusted to from about 1 to about 13.5 with a suitable acid or base. The resulting stable aqueous solutions are useful for depositing the water soluble organosilane on a variety of substrates to, among other things, serve as coupling agents, waterproofing agents and to render substrates antimicrobial and algicidal depending upon the nature of the organosilane.