I claim the ornamental design for a barbecue grill, as shown and described.
FIG. 1 is a perspective view of a barbecue grill, showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines shown in the drawings are for the purpose of illustrating unclaimed portions of the barbecue grill and form no part of the claimed design.