* Wheat falls as traders ready for USDA report on Monday

* Corn set to finish quarter down 12 pct

* Soybeans stocks seen at more than 30-year low

By Colin Packham

SYDNEY, June 30 (Reuters) – U.S. wheat futures, set to post its biggest quarterly loss in three-years, fell on Monday as traders squared positions ahead of a U.S. Department of Agriculture report expected to show domestic stocks at a six-year low amid ample global supplies.

Corn fell as the front-month contract was poised to finish the quarter down 12 percent, the sixth quarterly slide in the last seven, while soybeans was set to finish the quarter down 2.5 percent despite U.S. stocks seen as hitting a 37-year low.

Chicago Board of Trade front-month wheat fell 0.43 percent to $5.82-3/4 a bushel, having closed down 0.34 percent on Friday.

September wheat futures, the most actively traded contract, fell 0.3 percent to $5.92 a bushel, having firmed 1.54 percent on Friday.

“The market finished up more than 1 percent on Friday and all we are seeing today is some squaring of positions ahead of the USDA report tonight,” said Andrew Woodhouse, grains analyst, Advance Trading Australasia.

Spot wheat is down 16.4 percent for the quarter, the biggest slide in three years as global supplies offset tighter U.S. stocks, projected to be shown at a six-year low by the USDA.

Yields from the harvest of hard red winter wheat in the U.S. Plains improved slightly in the last week as combines rolled into central and northern Kansas, the top producer of the grain, a weekly harvest report said.

Front-month corn fell 0.56 percent to $4.40-1/4 a bushel, having edged higher modestly in the previous session.

Analysts projected June 1 corn stocks at 3.722 billion bushels, 35 percent above a year earlier and the largest in four years. Wheat stocks were seen at a six-year low of 598 million bushels, 17 percent below last June.

November soybeans fell 0.53 percent to $12.21-1/2 a bushel, having closed down 1.3 percent on Friday.

Relentless demand from exporters and processors likely thinned U.S. soybean stocks by June 1 to the lowest since the 1970s, but farmers have responded by planting their largest-ever soy crop this season, analysts expect government data to show on Monday. {ID:nL2N0P50ZJ]

Grains prices at 0304 GMT Contract

Last

Change Pct chg Two-day chg MA 30 RSI CBOT wheat

592.00

-1.75 -0.29%

+1.24%

613.31 41 CBOT corn

440.50

-2.50 -0.56%

-0.51%

455.13 38 CBOT soy

1221.50

-6.50 -0.53%

-1.83%

1264.12 48 CBOT rice

$13.53 -$0.03 -0.22%

+0.48%

$13.80 46 WTI crude

$105.46 -$0.28 -0.26%

-0.26%

$104.72 46 Currencies

Euro/dlr

$1.364 $0.000 -0.03%

+0.24% USD/AUD

0.941

0.000 -0.05%

+0.05% Most active contracts Wheat, corn and soy US cents/bushel. Rice: USD per hundredweight RSI 14, exponential (Reporting by Colin Packham)