Abstract: Provided is a glass reinforced molding composition which comprises a mixture of (i) a copolymer of trioxane and a cyclic ether or cyclic acetal or linear polyacetal, (ii) a terpolymer of trioxane, a cyclic ether and/or cyclic acetal and a diglycide of the formula ##STR1## wherein Z is a carbon-to-carbon bond, an oxygen or oxyalkoxy of 1 to 8 carbon atoms or an oxy-poly(lower alkoxy), and (iii) a glass reinforcing agent. The resulting glass reinforced composition exhibits improved property retention, e.g., of properties such as tensile strength.