There is no need to select anything. Also, in one place your code refers to 'randoms', but then uses a different name (object) to output the value. Such inconsistencies can lead to serious problems in a more complex macro. Try:
Code:
Sub Randoms()
Dim Rng As Range
For Each Rng In Range("A1:F20")
Rng.Value = Rnd()
Next
End Sub
PS: When posting code, please use the code tags. They're on the 'Go Advanced' tab.