After a bit of googling around, I don't envy your task.
If your Grosler is of German/Austrian/Swiss origin there could be numerous variations to check out. It may be one of many, many variants originating as a name given to a big person: “Gross”, “Gros” or “Grose”. The name apparently became so common (like “Schmidt”) that people were encouraged to add suffixes (e.g. “Grossman”, meaning “big man”; Grossbauer” (“big farmer”); and “Grosslicht” (“goodlight”); and many, many others.
To further complicate matters, there are also (mis)spelling variations that add an “o” (“Groosler” etc) and ones that drop the “r” (like “Goos” and “Goss”) with and without suffixes like “man” and “ler”. (While “Gross” and “Goss” have completely different origins, because of spelling and pronunciation variables you end up with crossovers.) I’ve also seen “
Von Grossler” (plus variants).
Numerous Austrian spelling variations (Grießler, Griessler, Grassler, Graßler, Grössler, Grossler, Griesler, Grässler, Gressler, Großler, Grasler, Greßler, Gräßler, Grissler and Grösler) are given on this site:
http://namenskarten.lima-city.at/austria/Größler/Perhaps searches using wildcards like *Gr*sl* or *G*sl* will capture many of the variants.
Good luck!
Peter