A stabilizer composition for polymeric organic materials, said stabilizer composition comprising: i) a stabilizing amount of an ultraviolet light absorber (UVA) selected from the group consisting of: orthohydroxyphenyl triazine compounds; benzoxazinone compounds; and mixtures thereof; ii) a stabilizing amount of a co-active agent selected from the group consisting of C 12 -C 60 monohydric alcohols; alkoxylated alcohols or monoalkyl ethers thereof; alkoxylated esters of fatty acids; sorbitan esters or ethoxylates thereof; mono- or polyglycerol esters having from 1 to 20 glycerol units or alkoxylates thereof; alkoxylated fatty amines, esters thereof, or salts thereof; sugar esters; alkoxylated fatty amides; ethylene oxide/propylene oxide copolymers; and mixtures thereof, wherein the co-active agent is present at from 1 wt.% to 99 wt. % based on the total weight of the stabilizer composition; and iii) a stabilizing amount of a hindered amine light stabilizer compound (HALS) comprising a functional group according to Formula (II): wherein R 31 is chosen from: hydrogen; OH; C 1 -C 20 hydrocarbyl; -CH 2 CN; C 1 -C 12 acyl; or C 1 -C 18 alkoxy; R 38 is chosen from: hydrogen; or C 1 -C 8 hydrocarbyl; and each of R 29 , R 30 , R 32 , and R 33 is independently chosen from C 1 -C 20 hydrocarbyl, or R 29 and R 30 and/or R 32 and R 33 taken together with the carbon to which they are attached form a C 5 -C 10 cycloalkyl; or a functional group according to Formula (IIa): wherein m is an integer from 1 to 2; R 39 is chosen from: hydrogen; OH; C 1 -C 20 hydrocarbyl; -CH 2 CN; C 1 -C 12 acyl; or C 1 -C 18 alkoxy; and each of G 1 -G 4 is independently chosen from C 1 -C 20 hydrocarbyl; or mixtures of HALS compounds having functional groups according to Formula (II) and Formula (IIa). i) a stabilizing amount of an ultraviolet light absorber (UVA) selected from the group consisting of: orthohydroxyphenyl triazine compounds; benzoxazinone compounds; and mixtures thereof; ii) a stabilizing amount of a co-active agent selected from the group consisting of C 12 -C 60 monohydric alcohols; alkoxylated alcohols or monoalkyl ethers thereof; alkoxylated esters of fatty acids; sorbitan esters or ethoxylates thereof; mono- or polyglycerol esters having from 1 to 20 glycerol units or alkoxylates thereof; alkoxylated fatty amines, esters thereof, or salts thereof; sugar esters; alkoxylated fatty amides; ethylene oxide/propylene oxide copolymers; and mixtures thereof, wherein the co-active agent is present at from 1 wt.% to 99 wt. % based on the total weight of the stabilizer composition; and iii) a stabilizing amount of a hindered amine light stabilizer compound (HALS) comprising a functional group according to Formula (II): wherein R 31 is chosen from: hydrogen; OH; C 1 -C 20 hydrocarbyl; -CH 2 CN; C 1 -C 12 acyl; or C 1 -C 18 alkoxy; R 38 is chosen from: hydrogen; or C 1 -C 8 hydrocarbyl; and each of R 29 , R 30 , R 32 , and R 33 is independently chosen from C 1 -C 20 hydrocarbyl, or R 29 and R 30 and/or R 32 and R 33 taken together with the carbon to which they are attached form a C 5 -C 10 cycloalkyl; or a functional group according to Formula (IIa): wherein m is an integer from 1 to 2; R 39 is chosen from: hydrogen; OH; C 1 -C 20 hydrocarbyl; -CH 2 CN; C 1 -C 12 acyl; or C 1 -C 18 alkoxy; and each of G 1 -G 4 is independently chosen from C 1 -C 20 hydrocarbyl; or mixtures of HALS compounds having functional groups according to Formula (II) and Formula (IIa). m is an integer from 1 to 2; R 39 is chosen from: hydrogen; OH; C 1 -C 20 hydrocarbyl; -CH 2 CN; C 1 -C 12 acyl; or C 1 -C 18 alkoxy; and each of G 1 -G 4 is independently chosen from C 1 -C 20 hydrocarbyl; or mixtures of HALS compounds having functional groups according to Formula (II) and Formula (IIa). <EOS>