#Mathematica, 62 bytes

BlockMap[Fold[#+##&,Join@@#]==48879&,#,{4,4},1]~Position~True&

Returns all positions of the BEEF matrix, 1-indexed. The input must be a matrix of binary digits. The x and y in the output are switched, though.

Mathematica, 62 bytes

BlockMap[Fold[#+##&,Join@@#]==48879&,#,{4,4},1]~Position~True&

Returns all positions of the BEEF matrix, 1-indexed. The input must be a matrix of binary digits. The x and y in the output are switched, though.

#Mathematica, 62 bytes

BlockMap[Fold[#+##&,Join@@#]==48879&,#,{4,4},1]~Position~True&

Returns all positions of the BEEF matrix, 1-indexed. The input must be a matrix of binary digits. The x and y in the output are switched, though... (if this is a problem, I'll fix it)

#Mathematica, 62 bytes

BlockMap[Fold[#+##&,Join@@#]==48879&,#,{4,4},1]~Position~True&

Returns all positions of the BEEF matrix, 1-indexed. The input must be a matrix of binary digits. The x and y in the output are switched, though.

#Mathematica, 62 bytes

BlockMap[Fold[#+##&,Join@@#]==48879&,#,{4,4},1]~Position~True&

Returns all positions of the BEEF matrix. 1-indexed. The x and y are switched, though... (if this is a problem, I'll fix it)

#Mathematica, 62 bytes

BlockMap[Fold[#+##&,Join@@#]==48879&,#,{4,4},1]~Position~True&

Returns all positions of the BEEF matrix, 1-indexed. The input must be a matrix of binary digits. The x and y in the output are switched, though... (if this is a problem, I'll fix it)