In a large skillet over medium heat, brown ground beef, sausage and onion until sausage is no longer pink.

Drain any oil from the meat and break meat up with a potato masher until crumbly.

In a large microwave safe bowl place cheese cubes, diced tomatoes with juice and milk.

Microwave on high for 2 minutes.

Stir to blend any cheese that has melted.

Continue to microwave for 30 second intervals, stirring after each one until cheese is completely melted.

Fold in beef/sausage mixture, stirring to blend.

Serve immediately with tortilla chips.