I claim the ornamental design for a baking parchment with gridlines, as shown and described.
FIG. 1 is a perspective view of a baking parchment with gridlines, showing my new design; and,
FIG. 2 is a top plan view thereof.
The additional sheets of the baking parchment illustrated in FIG. 1 are included for the purpose of illustrating the invention in use on a perforated roll of such parchment, and form no part of the claimed design. The target indicia illustrated on the baking parchment illustrated in FIGS. 1 and 2 are included for the purpose of illustrating one such possible indicia, and form no part of the claimed design.