In 12-inch nonstick skillet, heat oil over medium-high heat. Add onion, mushrooms and bell peppers; cook 4 to 5 minutes, stirring frequently, until vegetables are tender crisp. Add milk, hot water and sauce mix (from Hamburger Helper™ box); stir to combine. Stir in uncooked pasta (from Hamburger Helper™ box) and broccoli. Heat to boiling, stirring occasionally. Reduce heat; cover and simmer about 10 minutes, stirring occasionally, until pasta is tender and sauce is thick. Remove from heat; stir in tomatoes and sour cream.