You have to pass the array into the COM object.
In the Init() of the COM class, add this line to make sure the VFP object knows to treat parameters by reference.

SET UDFPARMS TO REFERENCE

Then make the call from the ASP page like this: (VBScript)

** ASP code
Set oCOM = Server.CreateObject("myvfpdll.myclass")
Dim aArray(0)
oCOM.DoSomething aArray
** aArray now has 4 elements

** VFP code
** myclass.DoSomething
LPARAMETERS taArray
EXTERNAL ARRAY taArray
DIMENSION taArray(4)
taArray[1] = "this"
taArray[2] = "is"
taArray[3] = "a"
taArray[4] = "test"

The ASP page (using VBScript, at least) will still treat the array as 0 based, but it will be (Row,Col) as in VFP, not (Col,Row)