Matching Information Across Worksheets

Hello,
I am experiencing trouble with a monster workbook. Can I ask someone to help me with the following:

I have a workbook with purchases by quarter (four tabs, each a separate quarter) - total 90,000 lines. Each item purchased is listed in separate rows by date of purchase & quantity per order; therefore, the same item(s) may be listed twice or as many as 20 lines per tab. One column is the item identifier, one column is the item description, one column is the package quantity and one column the package cost. How do I use a single worksheet to locate/list each time the identifier, description & package size match, then count the total quantity purchased per matching items?

I hope I explained it properly. Thank you for your help
Barry