What would be the most fastest way to copy a 2 dimensional
array (rXc) to a range starting at cell A1?

Let's say your array's name is ARR. Assuming your array is one-based (not
zero-based), then this line of code will do what you asked for...

Range("A1").Resize(UBound(Arr, 1), UBound(Arr, 2)) = ARR

Rick Rothstein (MVP - Exce)