SSRS report running very slow but query is very fast in SSMS

I am running a very basic report. I am just retrieving some data from a table and I am using a parameter in the Where clause of the query. The query runs fast (in less than 5 secs) if I hardcode the parameter in the SSRS query but if it's left as a dynamically chosen parameter the query takes over 5 minutes to render. I have read a little about "Parameter Sniffing" but I am not sure if that applies to my case since I am only using a TSQL query and not a SP.

Any feedback would be appreciated.

PS: My query looks like below:

Select Col1, Count(*)
From Tbl1
Where Col2 = @Para1
Group By Col1

KK