C# - Speeding Up LINQ To SQL Code?

I am developing an ASP.NET where I need to display each purchase for every account in a GridView (so basically each purchase links to an account).

The problem is, we have over 6000 suppliers (granted, these can be filtered down to around 1000 which the customer will usually do), each of whom will have a few transactions. So you can imagine the time it takes to bind this data is very long - in fact, occasionally the SQL server times out. Sadly I cannot use paging, as all the data needs to be displayed in one page.

What I'm doing is similar to the code below (not at my machine so can't copy exactly)

IEnumerable<Account> accs = (from s in dc.Accounts select s);
foreach (Account acc in accs)
{
IEumerable<Purchases> purchs = (from s in dc.Purchases where s.AccountID == acc.ID select s);
double 30daysval;

[Code].....

Is there a faster way of doing this, perhaps using join's in LINQ or something? I know this may be a bit hopeless seeing as the data involved is huge, and that displaying a couple of thousands rows on a single page is fairly absurd, but that's what I've been told to do...